Abstract: Shape deformation of the fruits of Cuiguan, Qingxiang, Xueqing, Yuguan and Huangjin pears was investigated. The results showed that the irregularity occurred commonly at an average defective rate of 46.02% and varied with varieties in the flower- and fruit-thinning cultivation. For instance, the defective rate for Huangjin was the lowest (33.57%) followed by Qingxiang (43.78%). Compared with Cuiguan, Yuguan and Xueqing,the deflective fruit rates of Huangjin and Qingsiang were lower,the difference were extremely significant and significant respectively. On the other hand, there was no difference on the shape deformation among Cuiguan, Yuguan and Xueqing pears. The deformation appeared to start during enlarging of the young fruits, and a considerable number of deformed fruits had already existed by then. The pear deformation developed in three stages, namely, the slow growth, rapid expansion and relative stability.The good shape of young fruit in the early developing is the base of keeping growing symmetrically in the follow-up development.The progression from upward growth to downward is the crucial period of controlling fruit growing unsymmetrically.