CHIANG CHING-KUO, president of Taiwan, died last week at age 77 on the island to which his father, Generalissimo Chiang Kai-shek, brought the Kuomintang Party after its defeat in China's civil war in 1949. The son had neither the compelling personality nor the dramatic career of the father, whom he succeeded in 1975. Serving most of his term after the United States "derecognized" Taiwan in 1978, he was little known in this country. His achievements for Taiwan, however, were considerable.

President Chiang managed Taiwan's traumatic but successful recovery from the shock of almost universal diplomatic "derecognition" when Beijing came fully onto the world stage in the 1970s, and its subsequent transit toward a future which is by no means assured but which it is far better situated to navigate than many people expected a decade ago.

Besides looking to Taiwan's defense, he strengthened Taiwan's economic sinews and trading connections, giving his country power in a usable dimension and providing a stake in national success to the island's citizens, including the 80 percent who are Taiwanese. He kept Taiwan's political liberalization moving ahead of the popular agitation that has swept and shaken other Asian authoritarian outposts. His style is suggested by his quick, dull and constitutional succession by Vice President Lee Teng-hui, 64, a PhD in agricultural economics from Cornell and a native Taiwanese.

President Chiang preached his father's doctrine of one China, eventual recovery of the mainland and anticommunism. But quietly, if hesitantly, he adapted. Just as Taiwan has widened its American political base and is no longer regarded as merely the pet of a ''China lobby,'' so it has moved in the direction -- there's a long way to go -- of accommodation with the People's Republic.

The mainland's modernizing urge has led it to emulate some of the free-enterprise ways that have made Taiwan a development exhibit. Trade with the mainland is important and increasing, and Taiwan now openly allows family visits there. China met Taiwan's changing of the guard not with a pronouncement of anathema but with the Communist Party chief's condolences and respects for President Chiang's commitment to one China. There is a common interest in keeping alive the dream of reunification and meanwhile of heading off Taiwanese independence sentiment. This is the substantial legacy of President Chiang.