Abstract: In order to study the feasibility of the in-service dry coupling ultrasonic test technology for rocket jet, the principle of the dry coupling ultrasonic testing was analyzed, and both the manual and automatic testing methods were applied to test the rocket jet specimen and the rocket jet parts in service. The results show that the debond defect, whose normal size is larger than 20mm, can be found using the two kinds of the dry coupling ultrasonic testing methods. It satisfies the quality request of the rocket jet being tested in service. It is the same to the manual testing and automatic testing in the ability of finding defect. And there is difference between the two testing methods in the operation and efficiency. The study is useful for testing rocket jet in service.