The Reagan administration, in a gesture of accommodation to be carried to Peking next week by Secretary of State Alexander M. Haig Jr., has decided to permit China to purchase additional American technology with potential military uses.

The decision, evidently made at a National Security Council meeting Thursday, was disclosed yesterday by a top State Department official during a briefing for reporters on Haig's forthcoming journey.

The official described the U.S. action as a decision "in principle" to be more flexible in approving sales of advanced technology, including items that have potential use in the military field.

"China's status will be changed" in the export control process, said the top official, who did not permit use of his name.

While loosening the reins on transfers of technology, no decision has been made to sell armaments to Peking at the present time, the official said.

The administration's decision evidently is intended to symbolize its desire to advance the strategic relationship with China about which Haig often has spoken in public. But its practical effect is unclear, because implementation is to be on a case-by-case basis in response to Chinese sales requests.

In a gesture to China following the Soviet invasion of Afghanistan, the Carter administration last year created a special export control category, designated "Category P," to make possible Chinese purchases of items denied to the Soviet Union and most other communist countries.

However, the Chinese have complained that some of their most important requests, including purchase orders for a highly sophisticated computer to assist in next year's census, have been long delayed or even stymied within the U..s bureaucracy.

It remains to be seen to what extent the new decision will mollify China's political leaders, who have expressed grave concern about a possible administration shift toward greater U.S. support and recognition for Taiwan. a

Haig's mission is intended in part to "clear the air" between Washington and Peking at this early stage of the Reagan administration, according to the State Department briefing.

Part of this dialogue, however, will concern the continuing sales of U.S. weaponry to Taiwan, an arms relationship China has consistently rejected. These U.S. sales under the Taiwan Relations Act, to which China also objects, will continue, according to the briefing.

The official said no decision has been made about possible sale of a high-performance jet fighter to Taiwan. He hinted that the future level of U.S. military sales to Taipei, currently described as $700 million to $800 million per year, would be influenced by Chin's policies, saying Washington's assessment of Taiwan's defense needs would hinge on "the level of tension in the [Taiwan] straits."

Haig also will tell the Chinese leadership, according to the briefing, that the administration stands by former vice president Walter F. Mondale's pledge of as much as $2 billion in Export-Import Bank credits to finance Chinese economic development. Money to make good this pledge is threatened by the administration's economy drive.

While the official declined to disclose details, he said Haig expects to discuss a possible trip to China by President Reagan.

The secretary of state is scheduled to leave late Wednesday on the 15-day Pacific journey to Hong Kong and China, to the Philippines for meetings with Southeast Asian and Japanese foreign ministers gathered there and to New Zealand for conferences with Australian and New Zealand foreign ministers.