Abstract: The preventative maintenance programs for VVER nuclear power plant stipulate that control rod assembly friction force tests should be carried out during outage. Based on the important role of the friction force test in the critical path of outage, the development of the friction force tests device was carried out. In this paper, the mechanical design and control system design of the test device are completed, and the automatic control of the full stroke of the test is realized, and the automatic processing and real-time display of the measured datas are realized. The filter algorithm is used to eliminate the possible abnormal datas and improve the intelligence of the test device. The test device has been successfully applied in many outages, which improves the working efficiency and safety, reduces the radiation dose and labor intensity of the workers.