Abstract: A new technology of microwave drying of iron precipitate slag from zinc hydrometallurgy was studied．The effects of microwave power, material mass, microwave drying time and their interaction on the relative dehydration rate of iron precipitate slag were investigated by means of the response surface (RSM) centra composite design (CCD). The prediction regression equation between dehydration rate and each factor was established, and the optimized process parameters were obtained in microwave power of 1000 W, material mass of 50 g, microwave drying time of 12 min. The corresponding relative dehydration rate of the iron precipitate slag is 98.81%．The measured value is close to the predicted value. The results show that the prediction model is accurate and effective, the optimized process is reasonable and feasible.