According to the test requirements of the wheel loader pilot valve, the assembly test controlled by PLC and step motor was developed. The structure, working principle and control requirements of the assembly test were introduced. On this basis, the software developments of PLC and LabVIEW were carried out. The actual application shows that the control system can meet the test requirements of pilot valve, and the system runs well, the test efficiency is high, the data acquisition and processing is reliable and effective. It provides experimental support for test，design and maintenance of product leaving factory．