To determine fatigue life of Loader transmission and to analyze machine power for different user, the torque loads of wheel loader transmission are tested and calibrated with the method of four sections per cycle. The disturbed signals are filtered by low-passed filter, and anomalous spikes are eliminated with the NSOFT. And contrastively analyzes the disposal effect of signal, then acquires pure random load-time course. It concludes that one Hz of the low-pass filter frequency is suitable, and the test signal is in line with the actual work of Loader. These provide the base for getting load spectrum and virtual test on wheel loader transmission.