Toughening of Poly(styrene co methacrylic acid)(SMAA) by bisphenol A Polycarbonate (PC) is studied by means of blending. The morphology, structure and methanical properties of the blend are measured and analyzed by DSC, SEM, FT IR and mechanical test respectively. The results show that SMAA/PC is a partial miscible system and there exist hydrogen bonds interaction. In a certain range of the blend ratio, the particles of two polymers are very finely and uniformly distributed. By comparison with SMAA, the impact strenth of the blends are notably improved.