Abstract: The separating planting mechanism with planetary elliptic gears of high performance rice transplanter made in Japan could not meet the agronomic demand in South China. In this paper, the kinematics model of the separating planting mechanism with planetary elliptic gears was established on the basis of the transmission analysis of elliptic gears, and the software for optimizing structure parameters was programmed by means of Visual Basic in order to find out a set of proper parameters easily. According to the different agronomic requirements of South China and North China, with two different planting arms, the separating planting mechanism was optimized and developed. With the help of theoretical model, the performances of three different separating planting mechanisms (with planetary elliptic gears, with planetary eccentric gears and with crank rocker) were compared.