The response surface methodology experiments were used to optimize ultrasonic-assisted extraction of seeding-watermelon seeds oil and oil's fatty acid composition were analyzed. The optimal extraction conditions were as follows: particle size 60 meshes,solid liquid ratio 1∶ 8,ultrasonic frequency 36 k Hz,ultrasonic temperature 50 ℃,and ultrasonic time 40 min. Under these optimized extraction conditions,the oil extraction rate of seeding-watermelon seeds was 23. 59%,the linoleic acid extraction amount was 180. 03 mg / g. By using the gas chromatographic analysis,the main unsaturated fatty acid compositions of seeding-watermelon seeds oil were oleic acid,linoleic acid,meanwhile the polyunsaturated fatty acids contained a small amount of γ-linolenic acid,EPA and DHA. Among them the linoleic acid content was the highest of all.