The invention discloses a method for testing service life of a friction clutch of a torque backlash type gearshift mechanism. The method comprises the following steps of S1, detaching one or a plurality of members in a low-speed-gear driving tooth, low-speed-gear driven tooth and an overrunning clutch; S2, connecting an input shaft with a driving motor, and locking an output shaft; S3, setting a rotating speed parameter and a highest cycling number-of-times Nmax of the driving motor; S4, setting testing end conditions of a, time ratio of a period in which Tm is smaller than or equal with Tdn_min/i2 in a rotating speed increase period of the driving motor exceeds deltax, wherein Tm is the torque of the driving motor, Tdn_min is a gear shifting-down torque allowable range lower limit value,i2 is a high-speed-gear transmission ratio of the torque backlash type gearshift mechanism, and deltax is a preset value; b, the cycling number-of-times Nx of the driving motor satisfies a condition of Nx=Nmax; and S5, starting the driving motor, and ending testing when a random condition the step S4 is satisfied. The method according to the invention has advantages of simplifying a testing deviceand a testing flow, reducing testing cost, and improving testing efficiency and testing precision.