D, L-lactic acid was polymerized through melt polycondesation in order to prepare poly(lactic acid) with high optical properly. Polarimetry, FT-1R, DSC, 1H-and 13C-NMR were used to detect microstructure, molecular weight, and optical purity of poly (lactic acid) samples. Racemic PDLLA was prepared from D,L-lactic acid with Sn powder as catalyst or without catalyst. Both SnCl2/p-toluenesulfonic acid system and SnCl2/o-toluenesulfonic acid systern could be used as catalyst to obtain PDLLA with higher molecular weight(M,>20 000), lower dispersity (being 1. 1), and higher optical purity (70. 5%) due to excessive L-conformation units in polymer chain. Poly(lactic acid) with high optical purity prepared from D, L-lactic acid could effectively low the cost of poly(lctic acid) materials.