Abstract: In the 2^nd and 3rd nuclear fuel cycles of Unit 1,Unit 2 and Unit 3 in Yangjiang Nuclear Power Plant, , R bank acts frequently, seriously affecting the safety with operation of the unit. In this paper, the logic control principle of R bank and the loading of core are analyzed, and the transfer function of first-order inertia, lead lag and differential link is converted into difference equation. The theoretical calculation is carried out before the parameter is modified, and the temperature ±4℃ disturbance simulation test upon 87%FP power platform is carried out on the plant simulator. The test results show that the modified parameters are correct and can solve the frequent action problem of R bank. After the modification of the parameters for Unit 2, the R bank acts normally, and R bank action frequency is about 1 time per 2 days.