The invention provides a trimming method for an improved main trunk tree suitable for mountain peach planting. The trimming method is characterized in that trunk heading is performed in a sapling state (tree age equal to or less than 2 years), branches on the main trunk except for main branches are cut, the main branches can grow naturally till the length of the main trunk exceeds 1 m, then, side branches on the main branches are thinned every one branch, and long fruit branches are utilized for fruiting. After harvesting of peaches in season, the long fruit branches which fruit for the first time are thinned, and after 2-3 years of fruiting, the side branches on the main branches are thinned or retracted to replace the fruit branches. According to the trimming method, the problems of low yield and low fruit quality of other tree forms in the early stage can be effectively prevented, the trimming method is simple and easy to operate, plants can be reasonably and closely planted, early fruiting can be realized, and high yield can be achieved.