Abstract: Centrifugal molecular distillation equipment was employed for refining lactic acid. The effects of temperature and rotary speed of evaporating plate，distance from evaporating plate and temperature difference on the purity and yield of L-lactic acid were studied. The results indicated that the optimal conditions to refine L-lactic acid by centrifugal molecular distillation were obtained at the pressure of 0.1Pa，feed-in temperature of 50—70℃，evaporating temperature at 60—75℃，rotary speed of the evaporating plate of 700—900 r/min，distance from the evaporating plate of 20—30 mm and temperature difference of 40—45℃.The purity of L-lactic acid increased from 80% to 95%，accompanied by the yield of 70% under the optimized conditions.