Abstract: Keeping uniform distribution of electric field in high voltage equipment is an effective method to prevent the insulation materials from aging or failure. ZnO microvaristor/ silicone rubber(SiR) composites have been used in electric field grading structures for high voltage equipment due to the nonlinear conductance and dielectric properties. In this paper, ZnO/SiR composites with volume fraction of 5%~40% ZnO were prepared. The relaxation processes of ZnO/SiR composites with different volume fractions of ZnO have been obtained by using broadband dielectric spectroscopy(BDS) in the frequency range of 0.1Hz~1.0MHz and the temperature range of -40℃~160℃. Three kinds of relaxations have been found, i.e. β relaxation, IDE relaxation and α relaxation, which are caused by the movement of polymer branch chain, ZnO microvaristor, and the transition to viscous flow state of silicone rubber, respectively. By linear fitting the logarithm of IDE(intermediate dipolar effect) relaxation time and inverse of temperature, it reveals that the mechanism of IDE relaxation in ZnO/SiR composite is the migration and accumulation of thermally activated carriers in ZnO microvaristor. This work provides basic data for the relaxation process of ZnO/SiR composites and supplies reference for the application of ZnO/SiR composites in high voltage equipment.