Abstract: South indica rice was used for raw material and single factor experiment and BBD response surface methodology were applied to optimize the preparation technology of pure Rhizopus oryzae koji with saccharifying enzyme activity as an index.Three important factors ( culture temperature, culture time, inoculating quantity) that had effects on Koji saccharifying enzyme activity and the optimum preparation technology condition were studied.Result showed that the process conditions as follows: culture temperature was at 33 ℃, the inoculating quantity was0.6 m L / flask, and culture time was 115 h.In this condition, the predictive value of saccharifying enzyme activity was295.2 U / g. And this prediction was verified under the optimum culture conditions. It showed that the actual measured saccharifying enzyme activity was 290.5 U / g. The predicted and measured were basically in accordance, which was verified the model was reliable and practical.