Abstract: As significant part of the loader, the power of hydraulic system accounts for about 70% of the rated power of the engine. So it is important to improve the efficiency of hydraulic system. Currently, wheel loader's hydraulic system generally uses constant displacement pump, which is supposed to generate large energy consumption. Although some researches have been done to study the energy consumption of loader's hydraulic system, these studies are short of experimental results quantified. In order to analyze the energy consumption of wheel loader during working process, a three-dimensional (3D) model of wheel loader is built by Pro/E software, and then it is imported into the software SimulationX to build the kinetic model of the whole wheel loader. Meanwhile the simulation model of hydraulic system is built by the same software. The research based on hydraulic model is mainly on multi-way valve and priority valve. In multi-way valve case, a 3D model is built firstly and its parameters about throttling grooves are measured by Three-coordinate measuring machine. At last, the flow area of control valve can be obtained by combining corresponding calculation module. By integrating the simulation model of hydraulic system with the kinetic model, the co-simulation model of wheel loader is thus achieved. The precision of co-simulation model of the working device is verified through the comparison between simulation results and test results, and the energy consumption of the hydraulic system driving the working device in the work cycle is analyzed under positive and negative loading condition. The testing results show that, under positive loading condition, the power of working device accounts for about 32% of the total output power of pump, the energy loss in priority valve accounts for about 15% and the energy loss in multi-way valve's export, import and its center position totally accounts for about 49%. Under negative loading condition, the power of working device accounts for about 27% of the total output power of pump, the energy loss in priority valve accounts for about 16% and that in multi-way valve's export, import and its center position totally accounts for about 52%. For the efficiency under negative loading condition is lower than that under positive loading condition, it is better to avoid the operations under unbalance loading condition as much as possible. The important energy loss in loader's working hydraulic system using constant displacement pump is the large throttling loss of multi-way valves when loader's bucket is inserted into materials. The differential pressure drop between the outlet of pump and the inlet of cylinder remains about 2 MPa during a working cycle without considering high pressure relief loss. Additionally, unloading losses can be eliminated if a load-sensitive variable pump is used. The co-simulation model established in this paper can be used to predict and analyze the distribution of energy consumption and the energy-saving potential of working devices. The research methods can be used for further research and comparing the operating characteristics and energy consumption of different hydraulic circuits, and it also can be used to guide the design of the hydraulic system and its practical operation. Moreover, it can provide the basis for designing energy-efficient hydraulic control system of wheel loader.