0-3 PMN/EP composites were prepared with different PMN particle size of powder A(100~154μm), B(74~100μm), C(66~74μm), D(45~66μm) , E(7~35μm) and F(0.15~18μm) by resin casting method. Particle size has great effect on property of PMN/EP composite. SEM analysis indicates that PMN particles with small size dispersed more uniformly in epoxy resin. The dielectric constant and dielectric loss of 0.1PMN/0.9EP and 0.3PMN/0.7EP composites vary a little with the particle size increasing, but dielectric constant and dielectric loss of 0.4PMN/0.6EP increase rapidly. Dielectric frequency characteristics analysis suggest that the variation trend of dielectric constant with different particle size at frequency of 103～106 Hz are almost similar in 0.3 PMN/0.7EP composites, but the dielectric constant of 0.4PMN/0.6EP composite with larger particle size drops remarkably with the frequency increase.