The invention discloses a silicon-based monolithic integrated sonar array which includes a cantilevered sensing array structure, a sound-transparent jacket, and a support structure. The cantilevered sensing array structure is fixed on the support structure and in the sound-transparent jacket, wherein the sound-transparent jacket is filled with insulating dielectric oil, and the cantilevered sensing array structure is immersed in the insulating dielectric oil. The sound-transparent jacket is sealed and is treated with water tightness processing. The array can be applied into devices for underwater ultrasonic imaging, ultrasonic ranging, torpedo navigating, etc.