A power system of electric vehicle driven by in-wheel motors was studied. First, force conditions of the running electric vehicle driven by in-wheel motors were analyzed. Then, the in-wheel motors and lead-acid batteries were selected with a certain type electric vehicle driven by in-wheel motors as a sample. A power system model of electric vehicle driven by in-wheel motors was built and simulated based on ADVISOR. The simulation result showed that the selected in-wheel motors and lead-acid batteries could meet the design requirement. Finally, the electric frame car designed was tested to prove the reasonableness of the simulation.