Abstract: Taking the content of reducing sugar, the content of V C and the rehydration as the evaluating indexes, to improve the quality of dried daylily and optimize the daylily vacuum freeze - drying process , central composite design of the Design-expert was used in the vacuum freeze-drying process of Daylily. Regression mathematical model between the index and impact factors was built. Central composite design was used to optimize experiments design and connect with the optimum method of response suraface methodology. The results showed that the optimal parameters of vacuum of freeze -drying process were as follows:material loadage was 225g and heating plate temperature was 50℃.