The basket-type transplanter has the characteristics of punching a hole in the mulch film and planting the seedling simultaneously, and has been applied in the transplanting process of tomato seedling in Northwest of China. Mass loss of root lump is caused by collision between tomato plug seedling and planting device when feeding device of basket-type transplanter feeds the seeding to planting device. For this problem, maximum contact force equation of root lump was got after contact mechanics model of planting device built by hertziantheory and kinetic energy theorem;differential equation of motion for tomato plug seedling was got after collision model among root lump, stem and planting device built by impulse and impulse moment theorem respectively;then an objective function was built by using goal planning method between contact mechanics equation and differential equation of motion, and 72° was the optimal value for seedling angle when the angular velocity of planting device was 1.18rad/s and 1.31rad/s by using the objective function. The height of tomato plug seedling was 12cm after analyzing the relationship between collision point and drop angle of tomato plug seedling and movement velocity;it was benefit to reduce mass loss of root lump. The collision was elasticplastic between root lump and planting device by using speed camera test to observe collision movement between tomato plug seedlings and planting device, the second collision of tomato plug seedling happened when root lump and stem collided with planting device, which meant theoretical research methods were reasonable. The root lump crushing test was carried out with the optimized operating parameters under the condition of angular velocity of planting device was 1.18rad/s and 1.31rad/s, test results showed that weight loss of tomato plug seedling was 9.67% and 8.43%, respectively, which was better than the test results of other combinations of parameters.