China's northwest border - its frontier with India, Pakistan, Nepal, and the Soviet Union - is once again witnessing the flourishing trade that centuries ago gave it the name the ''Silk Road.''
But this time it is television sets, cars, trucks, and synthetic textiles that are being exchanged for the traditional silks, cottons, tea, tobacco, and grains.
This fall China has signed trade agreements with India, Pakistan, and Nepal. Its border trade with the Soviet Union is entering its second year, and in China's northwest Xinjiang Province, two crossings on the border with the Soviet Union were opened last year after they had been closed for more than two decades.
Using the road crossings at Turugart and Horgas, Chinese cotton, silk wool, hops, and cloths are being exchanged for Soviet construction materials, refrigerators, cars, trucks, and agricultural goods. The exchanges are covered under an annual state-to-state agreement negotiated each year between Moscow and Peking. The level of trade has more to do with political relations than local demands for products. This year's level for two-way trade has been set at $1.2 billion.
A trade pass with the Soviet Union and China's Heilongjiang Province was also opened last year, where bartering is believed to be less regulated. This allows locals to trade in furs, meat, cooking oil, timber, and agricultural goods.
Moreover, people can use trade passes to visit relatives. (This is also true for Nepal and Pakistan.) Until late last year, the Turkic ''minorities'' on either side of the Sino-Soviet border could only visit their relatives by using a prohibitively expensive route. A Chinese, for example, wanting to go across the border had to buy a plane ticket to Peking, then to Moscow, and then from Moscow to the border area. The reverse was true for a Soviet citizen.
China's trade with Pakistan has increased from a trickle of local goods in 1969 to more than $300,000 worth last year - largely because of a highway built in 1970 between Urumqi, the capital of China's Xinjiang Province, and Pakistan.
In September, a Sino-Pakistan agreement instituted regular exchanges across the border. Chinese silk, clothes, light industrial products, and tea constitute the 100 or so products trucked across the western Himalayas in return for Pakistani TV sets, synthetics, chemical fertilizer, razors, cigarettes, and dried fruit.
Although border trade with India is still pending the resolution of disputed boundaries which orginally caused the 1962 Sino-Indian war, a wide-ranging trade agreement signed in September - the first between the two countries since 1954 - is seen as the initial step in easing tension along the closed border.
The head of the Indian delegation to the trade talks, Abid Hussain, indicated the three-year agreement, which gave India and China the most-favored nation trading status with each other, could eventually lead to two-way trade as high as $1 billion worth in the next five years.
''It opens up the floodgates for trade between the Asian giants,'' Mr. Hussain said in Peking.
Since 1957, Tibetan herdsmen have been free to travel up to 20 miles into Nepal to trade their yak and goatskins for Nepalese grain. Last year, formal trade topped $5 million. And in October, Tibetan and Nepalese authorities formalized an three-year trade agreement, in which Tibetan wool, sheep, and handicraft products will be exported to Nepal, which will sell rice, wheat flour , cement, and rolled steel in return.