Abstract: The effect of ultrasonic pretreatment on alkali extraction process conditions of coral ginger starches and their components, particle shape and crystal structure were studied with coral ginger residue as the raw material and extraction rate of starches as the selection standard. The results showed that the optimal process conditions of ordinary alkali extraction were that the p H of alkali liquor was 10, the ratio of material to liquid was1∶9g/m L, the immersion temperature was 35℃ and the immersion time was 3h, and under these conditions the extraction rate, purity and average particle size of coral ginger starches were 45.37%, 85.12% and 23.06μm respectively. The optimal process conditions of alkali extraction after using ultrasonic pretreatment (the ultrasonic power was 600 W, the ultrasonic time was 100s) were that the p H value of alkali liquor was 10, the ratio of material to liquid was 1∶12g/m L, the immersion temperature was 30℃ and the immersion time was 2.5h, and in these conditions the extraction rate, purity and average particle size of coral ginger starches were 61.54%, 86.51% and 20.20μm respectively. Ultrasonic pretreatment had made the process conditions of alkali extraction to be improved, the extraction rate and purity of starches to be increased, the average particle size of starches to be decreased, but the particles morphology and crystal structure of coral ginger starches to be not changed, they were still round, long ovate, triangular ovate and type B crystal structure.