The main theory of generalized minimal residual algorithm(GMRES) and fast multipole method(FMM) are applied into the numerical solution of equations about virtual boundary element method(VBEM) to form the idea about the fast multipole expansion of multi-domain VBEM,which is applied to solve the composite structures of different materials.With the method,the complexities of operation and memory about solution of the equations would be made to be of linear proportion to the freedoms of the problem.Numerical examples are presented to demonstrate the feasibility,accuracy and efficiency of the method.