Abstract: A system and method for measuring a sludge moisture content by ultrasound are provided, which relate to the technical field of sludge detection. The system includes: a measuring container, configured to load sludge; a pulse signal generator, configured to generate a pulse signal; a self-transmitting self-receiving (STSR) transducer, disposed on an outer wall of the measuring container, and configured to transmit a first ultrasonic signal into the measuring container under an excitation of the pulse signal and receive a second ultrasonic signal reflected from an inner wall of the measuring container; and an upper computer, configured to build a first mathematical model among a reflection coefficient, sludge acoustic impedance, and wall acoustic impedance of the measuring container, and build a second mathematical model between the sludge acoustic impedance and the sludge moisture content.