Abstract: To study the mechanical property of fiber reinforced composite, Reuss-Voigt model and 3D fiber orientation simplified model were utilized to develop the prediction model for elastic modulus of random short fiber reinforced composite (RSFRC). By virtue of this model, elastic modulus of glass fiber reinforced PA6 composite is predicted. The tolerance between calculated results and the tensile test values is less than 5%, which testified the good accuracy of the prediction model for elastic modus of RSFRC.