The invention discloses a multi-gear distributed self-walking speed changing box used for a riding type lawn mower. The multi-gear distributed self-walking speed changing box comprises a speed changing box shell and an input shaft. A main shaft, an auxiliary shaft, an output shaft and an intermediate shaft which are arranged in parallel are assembled in the speed changing box shell. A main shaft fifth-gear gear, a main shaft fourth-gear gear, a main shaft third-gear gear, a main shaft second-gear gear, a main shaft first-gear gear, a main shaft neutral shaft sleeve and a main shaft reverse gear are fixedly assembled on the periphery of the main shaft through splines. An auxiliary shaft fifth-gear gear, an auxiliary shaft fourth-gear gear, an auxiliary shaft third-gear gear, an auxiliary shaft second-gear gear, an auxiliary shaft first-gear gear, an auxiliary shaft neutral shaft sleeve and an auxiliary shaft revere gear are connected and assembled to the auxiliary shaft in a sliding manner. The multi-gear distributed self-walking speed changing box used for the riding type lawn mower has a five-gear forward gear function, a neutral function and a reverse function, in addition, a planet gear mechanism is used for meeting different torsion distribution requirements on the left side and the right side during turning, various practical work condition requirements in different environments and load conditions can be achieved, operation is easy and convenient, and convenience and high efficiency are achieved.