MELBOURNE, AUSTRALIA — AUSTRALIA'S decision to allow about 40,000 Chinese students to stay on after the Tiananmen Square massacre six years ago is paying off: They are now helping Australians break into a $450 billion market. So argues a recent government report, touted in an influential business daily as the key to ''Vaulting the Wall of China.'' ''Asian Australians are helping us link up to do business in Southeast Asia,'' says Michael Backman, author of the study on Chinese business networks in Asia. ''Non-Asian Australians provide the capital. Southeast Asian Australians provide the networking skills and cultural empathy. We see them as fantastic economic assets to open doors.'' Most of Australia's 300,000 ethnic Chinese migrated to Australia within the last decade from various countries in Asia, according to the report. In Sydney, Chinese is now the most commonly spoken language after English. ''In world trade now you need foreign cultural skills to compete, and one way to get there is to value your ethnic minorities,'' says Mr. Backman in an interview. ''The Japanese and Germans will lose out in the long run because they don't value their own ethnic minorities.'' Australia does encounter its share of culture clashes, particularly in the rural areas. In a town southwest of Canberra, the capital, for example, storefronts display signs that proclaim ''This business is 100 percent Australian-owned.'' But this is still a far cry from Australia 25 years ago, when the government pursued a ''White Australia'' immigration policy. ''After World War II, Australia wanted to increase its population because of a fear of invasion from the north ... and set up a major immigration program, initially to draw people from Britain,'' says Andrew Struik, deputy director of the Bureau of Immigration Research. Language tests were used to keep those of the ''wrong'' race and color out. The policy was not abandoned until 1972. ''Just a generation ago, the White Australia policy was still a reality in all but the technical detail,'' said Prime Minister Paul Keating, as he opened the Global Cultural Diversity conference in Sydney last April. ''Now half of our immigrants come from Asia. The encouragement of cultural diversity is much more than an act of benevolence - it is an act of national self-interest,'' he added. Soft-spoken Joseph Zheng shrugs off the fact that he is now ''Exhibit A'' in the Australian government's campaign to prove that cultural diversity is good for business. Last month's report on business networks in Asia credits Mr. Zheng with helping Townsend Chemicals, a small Australian chemical company, break into lucrative Chinese markets. ''I'm now mentioned in lots of newspapers,'' he says. ''But I have yet to see a profit.'' ZHENG, a native of Shanghai, came to Australia in 1989 to study at the Royal Melbourne Institute of Technology. ''I couldn't get the skills I wanted in China, and Australia had the easiest visa policy,'' he says. After graduation two years ago, he started Pacifique Sino, a consulting business he runs from his home in Melbourne, to help Australian businessmen make contacts in China. ''I have family and friends in Hong Kong, Shanghai, and Malaysia,'' he says. ''I thought I could use these contacts to build a bridge for Australian companies.'' Townsend Chemicals, a Victoria-based company that makes adhesives for shoes, asked Pacifique Sino for help in locating Chinese shoe manufacturers. They now produce more than 3.1 billion pairs of shoes a year. ''We'd been trying to sell to China for years, but realized we couldn't do it by ourselves,'' says Townsend marketing director Tony Wilson. ''We needed help. You can't just pick up the yellow pages in China. You need local people with contacts and knowledge.'' The venture has been a success for Townsend, but has yet to provide an income for Zheng. ''Next time, I'll try to get paid earlier,'' he says. Zheng is unsure he'll be able to compete with Japanese and American rivals over the long run. ''They have the capacity to set up branch offices in China.... I have to fly back and forth. They'll always have an advantage over me, just sitting in Australia. ''The Japanese and the Americans have been very smart, very dynamic in China,'' he adds. ''Australians aren't yet very enthusiastic and dynamic. They tend to sit there until the [business] option is nearly past.'' His doubts are shared by some key Australian business leaders. John Prescott, CEO of The Broken Hill Proprietary Company, a mining company and the nation's biggest business, said that ''strengthening our presence in Asia'' is a ''national imperative'' against which all government actions should be measured. ''Our proximity to Asia is a major advantage. But timing is important - if we don't build on this advantage, others will establish a presence there and we will again follow in their wake,'' he told a Melbourne audience last month.