In the production of L-lactic acid, the residual sugar that were difficult to be used by the microorganism in the broth would lead to the increased sugar content in its commercial products,bringing lactic acid product deterioration because of Maillard reactions and thus hindering its large scale application.To reduce the residual sugar content, the effects of temperature, pH, nitrogen source concentration, glucoamylase and pullulanase addition on the degradation of residual sugar were investigated.In order to consume the residual sugar as possible, fermentation was usually maintained a long stage even after cell growth and lactic acid production ended (phase II).The optimal conditions for reducing residual sugar content were temperature 50℃, pH 6.5, 20 g/L CSL and 0.5 g/L YE, and supplement with 125 U/mL glucoamylase after lactic acid producing ceasing.Under the optimized culture conditions, the minimum residual total sugar obtained was 2.27 g/L in comparison to 5.02 g/L in normal conditions.And we proposed a combined strategy that using the unsterilized hydrolysate and maintaining pH at 6.5 in phase II to reduce residual sugar content.In that case, the residual total sugar and reducing sugar decreased to 2.55 and 0.99 g/L, respectively,49.20 and 59.76% lower than these obtained with un-optimized culture conditions, which would save the cost and facilitate its industrial application.