Abstract: Based on the equations of the electric circuit and the magnetic circuit and analysis of the dynamic lifting process for the control rod drive mechanism（CRDM）,coupled magnetic-electric-mechanical equations both for the static status and the dynamic status are derived.The analytical method is utilized to obtain the current and the time when the lift starts.The numerical simulation method of dynamic analysis recommended by ASME Code is utilized to simulate the dynamic lifting process of CRDM,and the dynamic features of the system with different design gaps are studied.Conclusions are drawn as:（1） the lifting-start time increases with the design gap,and the time for the lifting process is longer with larger gaps;（2） the lifting velocity increases with time;（3） the lifting acceleration increases with time,and with smaller gaps,the impact acceleration is larger.