The Anli tribe, an aboriginal group in central Taiwan, had served as Yi-fan ("loyal barbarians") since the early Ch'ing they first helped put down a revolt by the T'ung-hsiao Tribe in what is present-day Miaoli County in 1699, and then played an important role in subduing a largescale rebellion of the aborigines in central Taiwan between 1731 and 1732. Consequently, they were rewarded with political positions and large strips of land. The land given to the Anli was located in the southern bank of the Tachia River. Because it was flat, fertile and had an abundant water supply, it attracted thousands of land-thirsty Chinese agricultural immigrants. What is most unusual was that the Anli tribe cooperated with the Chinese in developing their land on conditions favorable to the Chinese while most aboriginal groups struggled against invaders. Why did the Anli copperate with the Chinese? In this paper, the following four reasons are discussed. Firstly, the Anli needed the help of the Chinese to protect their newly acquired land, which had originally belonged to other aboriginal rivals or enemies. Secondly, the Anli attempted to prevent by the Chinese immigrants from incusions through cooperations with influential Chinese agricultural developers. Thirdly, Chang Taching, interpreter for the Anli Tribe, played a leading role in the program of cooperative agricultural development between the Chinese and the Anli. Fourthly, the Anli needed Chinese capital, technology and labor to develop a more advanced agriculture to satisfy their increasing demand for food, which was caused by shrinking hunting grounds and insufficient labor force. As the Chinese and Anli shared common interests, they cooperated in transforming the virgin lands of the Taichung Basin into paddy fields over a period of several decades.