This study presents a statistical two-scale method to predict the viscoelastic properties of composite materials with consistent random distribution of particles. The explicit formulation for predicting the effective viscoelastic relaxation modulus is given. At first, the Laplace transformation is used to the linear viscoelastic problem, the effective generalized relaxation modulus in Laplace domain for composites is derived. Then, the effective relaxation modulus in time domain is obtained by the least-square and inverse Laplace transformation. At the end of this paper, some numerical examples are given to validate that the presented method is feasible and effective.