Background: The electric heaters can regulate the pressure of the reactor coolant system

and are pressure boundary of the reactor coolant.The clad and sleeve of the heater are classified RCC-M class 1 and Seismic class 1I.Purpose: Model simplification and seismic analysis method of the heater are studied to support the structure design of the heater.Methods: The water around the electric heater is processed equivalently based on related theory.According to features of structure and support the finite element model of the heater is made by beam elements through finite element software ANSYS.Modal analysis and spectrum analysis for the heater are performed.Results: Analysis results are:（1） The nature vibration frequencies of the heater are respectively beyond of the frequency range which give significant values of acceleration.（2） During the SSE earthquake condition the structural strength of the heater meets the requirement.Conclusions: The seismic capability of the electric heater can be evaluated through analyzing its frequencies and stress intensity.