Prepolymer poly（L-lactide） （PLLA） and poly（D-lactide） （PDLA） having different optical purity were prepared by using lactide as monomer, lactic acid and stannous octoate as initiator and catalyst respectively, solid state polycondensation precursors were obtained by melting blend of PLLA and PDLA with similar optical purity. The effect of the optical purity of the prepolymer on the solid phase polycondensation products of stereocomplex polylactic acid was studied. The chain structure, molecular weight, crystal structure, dynamic mechanical properties and degradation properties of solid state polycondensation products were analyzed. The results show that the optical purity of prepolymer decreases with increase of the isomers content in the monomer. The reduction of the optical purity of the prepolymer reduces the content of both the homogeneous crystal and the stereocomplex crystal in the solid state polycondensation, thus promoting increase of the molecular weight of the solid state polycondensation products. When the optical purity of the prepolymer is reduced to 95.5%, the molecular weight of the solid state polycondensation product is the largest, and the molecular weight of the polymer is 97.6% higher than that of the polycondensation products without isomers. With decrease of the optical purity, the energy storage modulus, energy dissipation modulus, glass transition temperature of solid state polycondensation products are decreasing and the water absorption rate of solid state polycondensation products is increased.