How do non-superconducting inclusions influence the magnetostriction of bulk superconductors with viscous flux flow? This problem has still not been addressed in theoretical models. In the paper, a model is developed focusing on superconducting composites under zero-field cooling process, with the aim to investigate the effects of inclusion on the macroscale magnetostriction of composites, including the elastic properties, such as elastic modulus, volume fraction. Moreover, in order to evaluate the accuracy of the model, the theoretical values in the paper are compared with the results published in the literature, and the results show that the prediction of the model is quantitatively consistent with the data without viscous flux flow. It may be useful to researchers interested in the practical application of the superconductors.