The relationship between the biological characteristics of ornamental trees, the role of site environmental conditions and the purpose of greening design or garden cultivation is the main basis for plastic pruning. Only by fully understanding and mastering its related theories and carefully analyzing and studying can we make the most reasonable pruning decision and achieve good results. But pruning and plastic surgery should be carried out on the basis of a series of management, and pruning can't replace everything. Pruning also depends on the growth habits of ornamental trees and the garden environment. It is different from fruit tree pruning. To do this work well, we must first understand the basic laws of the growth and development of ornamental trees, then master some pruning principles, time and basic methods, and then adopt different pruning techniques according to different tree species.