Abstract: A study is concerned with the effects of three types of treated interfacts (carber fibers were treated-BS-6 and toughening layer-BS-1,water prevention layer-BSM2 was polyrrierized by means of a cold plasma) on interfacial and mechanical behaviour of carbon/epoxy composites.Comparative tests of interlaminar shear and fracture ware carried out under microscope. and S F.M.The results show that the interlaminar shear strength(ILSS) and fracturs toughness(K) of the three kinds specimens with treated interfaces are 30% and 40% higher than those of untreated specimens (BS-6) respectively.The reinforcing effect of SB-1 type specimens is optimum, the ILSS tis increased from 71MPa (SM-5)to 103 MPa(SB-1),and K is increased from 985 MPa√m to 1548 MPa√m, Furthmore,four types of microscopic interfaces and dynamic failure ara characterized by using SEM.The relationship of interfacial layer and mechanical properties as well as reinforcing mechanism are discussed.