An ultmsonic testing method for solid propellant of mcket engine is studied．The principle of ultrasonic feature scan imaging and the method of defect testing are presented．The ultrasonic feature scan imaging system for solid propellant is developed and the solid propellant is tested by using low-frequency combined transducers．The experiment shows that the ultrasonic feature scan imaging system can demonsttate the defects of solid propellant successfully by adopting amplitude imaging and depth imaging．