Fresh purple sweet potatoes (PSP) were used as raw material. The effect of combined drying on the free starch content of PSP granules was studied using the indexes of iodine blue value and anthocyanin content. And the correlation of combined drying on cell breakage and anthocyanin content was explored to reflex the effect of combined drying on cell breakage of PSP granules. The single factor experiment and response surface methodology were used to optimize the process parameters of the combined drying of PSP granules. It was concluded that the optimal process parameters of combined drying were hot air drying temperature of 70℃, intermediate conversion moisture content of 25%, and freeze-drying time of 7hours. The PSP granules prepared according to the optimal parameters had an iodine blue value of 10.25 and anthocyanin content of 16.23mg/100g. At this time, the PSP granules had the lowest iodine blue value, and the anthocyanin retention was better, which was higher than the anthocyanin content of PSP granules at the optimal level of single factor. It indicated that the combined drying could reduce the free starch content of PSP granules and avoid huge losses of anthocyanins, and proved that combined drying could prevent the cell breakage of PSP granules, and better maintain the cell integrity of PSP granules.