Abstract: On the basis of analyzing the micro-mechanical behavior, the macro-mechanical properties of 90 W heavy alloy and the effects of microstructural parameters（mechanical properties of matrix phase） on them have been calculated by computer numerical simulation. The mechanical properties of the alloy have been found to depend heavily on mechanical parameters of matrix phase. As the elastic modulus of matrix phase increases, the tensile strength of the alloy increases, while its elongation decreases. The tensile strength of the alloy has a maximum at the yield strength of matrix phase 800 MPa. When the yield strength of matrix phase<800 MPa, the tensile strength of the alloy increases with its increase, however, a opposite variation occurs when the yield strength of matrix phase> 800 MPa if the mechanical parameters except tensile strength of matrix phase are constant, both the tensile strength and the elongation of the alloy increase linearly with the increase of tensile strength of matrix phase, because the ductility of matrix phase increases with its tensile strength in this case. The elongation of the alloy is very sensitive to hardening modulus of matrix phase. As the hardening modulus increases the elongation of the alloy exponentially decreases.