Abstract: Poly (phthalazinone ether sulfone ketone) (PPESK) is a novel high performance thermoplastic material with out standing high temperature resistance and excellent mechanical properties，and therefore it is a very ideal candidate matrix for advanced composites. However，it s high melting viscosity of PPESK makes it difficult to melt-ingly process. In this paper，two well-known high performance thermoplastics，polyetherimide (PEI) and poly-ethersulfone (PES) were introduced to PPESK in order to reduce the melting viscosity of PPESK and improve the properties of composites. The effect of addition of PEI and PES on the resultant composites was studied. A series of unidirectional composites were made with PPESK and its PEI and PES blends as matrix and continuous carbon fiber (T700) as reinforcement. The solution prepregging method and hot-press molding method were used in preparation of the composites. The viscosities of polymer blends solutions were tested. The effects of the polymer blends matrix on the mechanical properties and fracture mode were studied by three points bending，interlaminar shearing，porosity and SEM test. The results show that the mechanical properties increase and the porosity decreases after blending PEI or PES in matrix. Addition of PEI and PES to PPESK results in an obvious transition of fracture mode.