The characteristics of the load and the change of the external load of the loader working device are studied. First, the external load identification model is established according to the relationship between the bucket hinge point force and the bucket tip force. Then, the three direction force pin sensor method and the boom section moment method are proposed. The load verification and dynamic load test of iron ore material are carried out on the prototype of the LW900K loader. The results show that the hinge point force could be gained accurately by these two methods, and the accuracy of the boom section moment test results is lower than that of the pin shaft sensor. Under the test equipment of iron ore material, the load of the working device appears in the time of digging and unloading materials. For the first time, the inertial impact load of LW900K loader is obtained through the test, and the peak load is about 400kN. The relationship between the mean, amplitude and frequency of the resultant force of the working device is obtained by the rain flow counting method. It is found that the distributions of load mean and amplitude obey normal distribution and Weibull distribution with three-parameter respectively. The load identification model could effectively solve the problem of the external load acquisition difficulty of loader working device, and the load time history data could be used as reference for the load spectrum and the analysis of the structural fatigue characteristics.