In order to study the load data model and load spectrum characteristics of the loader working device， the cross-section bending moment of the moving arm plate is introduced as the intermediate variable of the equivalent external load of the working device. Based on the measured load of LW900K loader， two equivalent load data models， namely the nuclear density estimation and parameter distribution estimation， are established. The fatigue test load spectrum is compiled and the fatigue damage verification test is carried out. The load spectrum of the working device can be obtained both by the kernel density estimation model and the parameter distribution model. Furthermore， the damage of parameter distribution model is much smaller while the fatigue life of the welding position calculated based on the load spectrum damage of the nuclear density estimation model is closer to the designed life of 3×104 hours. The results show that the damage results obtained by the nuclear density estimation model are closer to the reality. Based on the rainflow matrix， the load spectrum obtained by the nuclear density estimation model can make up for the weakening effect of distribution fitting in parameter distribution model on low frequency and large load， and can better reflect the real characteristics. The established data model and spectrum results provide a basis for fatigue life prediction and reliability test of loader working device.