Abstract: Epoxy resin matrix syntactic foam filled with glass microspheres is widely used in deep water buoy. In this paper, epoxy resin E51 is filled with hollow glass microspheres S60HS to prepare composite foam. The mechanical behavior of the hollow glass microspheres composite foam is analyzed by testing the mechanical properties of different volume fractions. Based on the microstructure characteristics of composite foam, the numerical model is established to study the influence of the diameter distribution of microspheres on the mechanical properties of composite foam. The results show that the predicted results of the finite element model with the logarithmic normal distribution of the microsphere diameter are in good agreement with the experimental data.