Abstract: For the plant operation which the safety margin is enough,it is positive to optimize the reactor trip signal set-point which could increase the efficiency of nuclear power plant.Overtemperature ΔT set-point optimization analysis is processed based on the accident of uncontrolled RCCA（Rod Cluster Control Assembly） bank withdrawal at power.Thermal-hydraulic sub-channel analysis code and transient analysis code are introduced into the research.The new set-point will influence the reactor trip time,DNBR and the limit of reactivity insertion rate.The result shows that the optimized overtemperature ΔT set-point leads to increase the operational margin and improve the economy efficiency when the safety margin remains large enough.The analysis provides the way to improve the reactor economy through optimizing the reactor trip signal set-point.