Effect of ultrasonic-assisted soaking conditions such as ultrasonic power, ultrasonic time and ratio of solid to liquid on the moisture content of paddy, percentage of head rice and pasting characteristics of parboiled rice were investigated. And then the ultrasonic-assisted soaking process was optimized by orthogonal experiment. Results showed that maximum percentage of head rice was 68.82% under the conditions of ultrasonic power 600 W, ultrasonic time 25min and ratio of solid to liquid 1 : ...