Abstract: Turing fabrication of composites, if the process parameters are selected unsuitably,voids will often occur in the composites.the Existcence of voids has great influence upon some mechanical properties of composites. The objective of this paper is to describe that void content haveinfluence upon the mechanical properties of unidirectional laminates, which include longitudinal and transverse tensile strengths and modui, flexure strength and modulus, in-plane shear strength and modulus,and interlaminar shear strength, etc.