American exports to the People's Republic of China of high-technology items that have a military as well as civilian application have been booming, according to a report issued yesterday by the National Council for U.S.-China Trade.

Export licenses for $249 million worth of such "dual-use" equipment -- the same technologically advanced material the United States now is seeking to prevent the Soviet Union from getting -- were granted in the first nine months of 1979.

Moreover, National Council President Christopher H. Phillips said in an interview that "the recent visit to the PRC by Secretary of Defense Harold Brown will give further impetus to this trend."

Phillips said that his impression after talking to both U.S. and Chinese officials is that "there won't be blanket approvals (for these technology items), but there will be increasing approvals on a selective basis of dual-purpose tehcnology."

The National Council is a semiofficial body set up after former president Nixon reopened relations with the PRC in 1973. It has continued its efforts to promote trade since the "normalization" of relations at the end of 1978.

U.S. officials had been debating most of last year how far to go in selling China sophisticated American technology. Included are advanced items designed primarily for peace-time use, but which also could have military application.

Examples are aircraft and spare parts, geophysical technology and equipment, electronic computing equipment, communications equipment (including integrated circuits) and electronic testing equipment.

The Chinese, naturally, have had a long shopping list, but U.S. officials tended to move cautiously so as not to offend the Soviet Union. But Phillips said that in the wake of the new cold war with the Soviet Union as a result of the invasion of Aghanistan, the caution -- most noticeable in the State Department -- is being modified.

Even before the latest Soviet aggression gave a new thirst to technology exports to the PRC, there was a school of thought that argued for more liberal treatment of such exports of the PRC.

A recent article in the council's authoritative "China Business Review" said, for example, that "it makes more sense to treat China as a developing country in need of advanced civilian technologies than a Communist one posing a direct military threat to the U.S."

As compiled by the Phillips organization, the bulk of the technology export licenses granted to the PRC in the first nine months of last year were for $168 million worth of aerospace equipment, aircraft and spare parts. The next largest category was $52 million of geophysicial technology and, primarily seismic surveying and processing equipment for oil and gas exploration. The third largest group was $10.3 million worth of electronic computers and equipment.

On his visit to China, Brown announced that the United States would sell the Chinese a communications ground station, which will give the PRC access to information from the U.S. resources satellite known as Landsat. Twenty other nations -- but not the Soviet Union -- have such ground stations.

Phillips predicted a steady growth of overall U.S-China trade, which has increased from about $1.2 billion in 1978 to $2 billion in 1979 and is projected at $2.5 billion to $3 billion for 1980. But he said that further expansion may be slow for the next couple of years, following the revision by the PRC of some earlier unrealistic production goals.

Phillips warned, however, that American manufacturers must be "more aggressive" to meet the competition from European and Japanese firms and "not look too closely at today's bottom line." Over the next few years, it will be a slow process of learning about China and making investments there, he suggested.