The wheel fatigue loading test machine by ZPMC of principle and structure were introduced. The problems existed during the debugging and commissioning of the machine were discussed, and the factors which influenced the loading function and accuracy of the machine were analyzed. The result shows that the loading machine equiped with system of horizontal and vertical movement can accurately locate the position of loading wheel quickly, and can satisfy different request in loading conditions, which has a guiding significance for research of loading fatigue test machine of second generation and for fatigue experiments of steel bridges.