Abstract: Abstract: Rape carpet seedling transplanter is suitable for the transplantation in rice stubble field. During the operation of planting mechanism, the seedling needle takes out the seedling block from feeder mechanism by cutting and tearing. Then the seedling block is carried and transported by the seedling needle to the point of seedling pushing. Once the seedling block separates the seedling needle automatically and falls to soil, it can not be planted into the soil. Therefore, it is urgent to effectively reduce the seedling separation phenomenon in mechanized transplanting process of rape carpet seedlings and improve seedling-standing quality. In this paper, a kinematics model of rape carpet seedling block in the process of seedling transportation is established. The friction coefficient, normal adhesion force and tangential adhesion force of the rape carpet seedling substrate are measured under different moisture content. In order to obtain the mass center, morphological characteristic parameters of seedling block are measured. By establishing the mathematical model of planting mechanism, the trajectory curve and acceleration curve of the tip point of the seedling needle are obtained. The relationship between the tip point of the seedling needle and the mass center of seedling block is established. Thus, the variation curve of resultant force for the seedling block in the process of seedling transportation is analyzed. The critical conditions for seedling separation in seedling transportation course which is divided into 3 stages are studied. The main factors affecting the occurrence of seedling separation are established. Combined with the high speed photography, effects are tested by the single factor test which consists of the substrate moisture content, planting mechanism rotation speed and longitudinal picking seedling-standing length on seedling separation rate. With the increase of planting mechanism rotation speed, the seedling separation rate is stable first and then increases gradually. With the increase of the substrate moisture content, the seedling separation rate reduces sharply and then remains stable. With the increase of the longitudinal picking seedling length, the seedling separation rate decreases first and then increases. The critical range of each factors obtained by single factor test are basically consistent with the theoretical analysis, which verifies the accuracy and feasibility of the model. Using the data analysis software Design-Expert 8.0.6, the response surface design (RSD) is applied to establish a mathematical regression model between main influence factors and inspection index by analyzing the substrate moisture content, planting mechanism rotation speed and longitudinal picking seedling length. The horizontal ranges of response surface test are selected through the influence result of the single factor test and operation requirement. And finally the optimal parameter combination is obtained. The optimal parameter combination is modified and verified through the same test method. When the moisture content of the substrate is 56.72%, and the rotation speed of the planting mechanism is 22 rad/s, and the longitudinal seeding length is 15 mm, the test results shows that the seedling separation rate is 1.52%, with an absolute error of 0.16 percentage points compared to the predicted value. This study may provide the technical support for the research and development of rape carpet seedling transplanting with great seedling-standing quality.