When Virginia A. Kamsky formed her own China trade consulting firm in 1980, she had three clients and was her company's only employee. She expected her business to remain at that level.

Today Kamsky Associates Inc. employs 40 people at offices in New York and Beijing. It represents some 65 companies, including Fortune 500 members Hershey Foods Corp. of Hershey, Pa., and Textron Inc. of Providence, R.I.Her client list also includes several European, Brazilian and Japanese firms. Six U.S. states have asked her to serve as their agents in China. In addition, she is negotiating with the Soviet Union and Mongolia about representing their enterprises in deals with the Chinese.

Such success is particularly remarkable for a 34-year-old woman dealing with a country still ruled largely by men either past or near retirement age. Ms. Kamsky, however, says that being a woman in China just wasn't an issue as long as you were competent.

Despite her youth, Ms. Kamsky already qualifies as an old China hand. She became interested in China at age 10 after reading such books as Pearl Buck's The Good Earth. She began studying Chinese a year later.

After majoring in East Asian languages at Princeton, she was hired by Chase Manhattan Bank for its global credit training program. I didn't even know what a bank does, she joked, but after the first three weeks I took to accounting like I did to Chinese.

She then went to work in Chase's Tokyo office, where she became involved in international trade and commodities. When Chase established a China division in the late 1970s, it put Ms. Kamsky in charge of the corporate side.

At the time, doing business with China was simpler in some respects. Nine state-owned import/export corporations controlled almost all of the country's foreign trade.

In recent years, however, China's provinces and cities have been given the freedom to cut their own deals with foreign companies, as have individual enterprises. That means companies such as Ms. Kamsky's must now negotiate with Chinese entities at both the central and local levels.

As a result, Ms. Kamsky may open offices in Shanghai and Guangzhou. San Francisco and Paris are also possible sites for new offices.

One of the deals she's working on now involves the potential sale of oil field equipment - manufactured by the Chinese under a co-production agreement with a U.S. company - to the Soviet Union, which in turn would pay back the Chinese by shipping them badly needed lumber.

Such projects take a long time, however. Her biggest deal, a $175 million real estate project in Shanghai, took six years to negotiate. It involves a $30 million equity investment by the developer, Atlanta-based John Portman & Associates, and $145 million in financing provided by a multinational 17- bank consortium, led by the Bank of China's Shanghai branch.