Abstract: The success rate of seedling selection and the erect degree of planting are important indicators to evaluate the planting quality in the process of pepper seedling selection. In order to explore the main factors affecting planting quality, the centroid of the hole tray seedlings was determined by the geometric method. The movement track of the hole tray seedlings was divided into four stages: seedling, picking, holding, and planting return. Force equations of the hole tray seedling centroid at the three key points of the seedling picking point were established to analyze the force of the hole tray seedlings centroid in the first three stages. MatLab was used to draw the force relation curve of the centroid in the process of seedling extraction and planting, and analyze the force situation and the position of the hole tray seedlings at key points. The results showed that the main factors affecting the planting quality were the hole tray seedling quality, the rotational speed of the mechanism, and the friction coefficient between clamping parts and the stem of the hole tray seedling. The critical conditions of each factor were obtained using the control variable method. The critical value of the hole tray seedling quality was 8.34 g. The critical speed of the mechanism was 105.4 r/min. The critical value of the friction coefficient of the clamping part was 0.147. According to the Box-Behnken response surface test, the optimal parameter combination of three factors were: the quality of the hole tray seedling was 5.20 g, the rotational speed of mechanism was 68 r/min, and the friction coefficient between clamping parts and the stem of hole tray seedling was 0.36. The optimal migration success rate was 91.04%.