This paper examines the controversy over the theory of precession during the late Ming and early Qing China. Ancient Chinese astronomy had a theory of precession different from Western astronomy. Early Chinese astronomers had noted the slight discrepancy, an ＂annual difference＂ （sui cha） , between the lengths of the tropical and sidereal years, that is between the time which elapsed from one winter solstice to the next and the time it took for the sun in its apparent annual circuit to return to a given position with respect to the fixed stars. They distinguished the ＇ celestial revolution＇ （ tian zhou ） from the ＂annual revolution＂ （ sui zhou ）, arguing that ＂ celestial heavens and the calendrical year are two different things （ tian zi wei tian, sui zi wei sui）. ＂ Western astronomers explain it by reference to a cosmology where celestial bodies are embedded in celestial spheres. Precession seen as a property of the motion of the whole cosmos, affects the positions of all fixed stars. The sphere of the fixed stars rotates on the axis of the ecliptic. During the period of late Ming and early Qing, the Western theory of precession was introduced into China by the Jesuits to explain ＂annual difference＂ （sui-cha）. This led to a violent controversy over the theory of precession between the Jesuit astronomers and some conservative Chinese officials. Jesuit astronomers used the theory of precession to demonstrate the superiority of the ＂new method＂ （ Western astronomy）, while some Chinese scholars used it to attack the Jesuits. At the same time, a number of Chinese astronomers who tried to bridge the differences between Western and Chinese astronomy took an open-mind- ed attitude towards the theory of precession. Mei Wending, trying to merge Western learning into Chinese system, re-interpreted the Chinese theory of sui eha in a way that would accommodate the Western theory of precession.