To study the seismic response of UHVDC insulators interconnection system under different actions of earthquake, the slipping fitting at the top of insulator is simulated as nonlinear spring, and the finite element method (FEM) is applied to analyze the seismic response. The data of acceleration, displacement and stress response at the critical parts of single and interconnected insulator system are obtained under multiple earthquake wave. The influence rules of tubular busbar on composite insulator are obtained from the comparison of dynamic responses of single and interconnected system. Comparing with equivalent single post insulator, results of the interconnected system show that the frequencies of interconnected system are increased; accelerations at the top of the insulator are much higher, and the displacement responses show much randomness; stresses at the bottom of the insulator are small and far less than the ultimate strength of composite insulator; the slippage distance of the fittings has great influence on the acceleration at the top of the insulator, and the effects of slippage on equipment must be taken into consideration in seismic design when the tubular busbar is used.