Abstract: The control rod drive line in this paper has been adopted in the reliability growth test, which was simulated as 1:1. This test was carried out in the operating condition of the practical reactor. The service life and failure event of the control rod drive line was tested by the reliability growth test. From the failure event, we can find out the failure reasons. Furthermore we can do targeted improvement by the failure reasons. After that the experimental verification was conducted once again on the basis of the original prototype of the control rod drive line multiplexing. The result of experimental verification proved that from the reliability growth test of control rod drive line, we can find out the potential shortfalls. Furthermore we can do targeted improvement by the potential shortfalls to improve the service life of the control rod drive mechanism.