In view of the deficiency of paying more attention to time (phase) and ignoring signal amplitude in the sound velocity measurement experiment, a signal measurement device was built in the water tank relying on the commonly used underwater acoustic detection equipment. The time difference and the peak value of voltage were obtained by oscilloscope, the sound velocity in water was calculated based on the measurement principle of time difference method, and the electroacoustic conversion was carried out to realize the synchronous measurement of sound velocity and sound pressure. The relative error between sound velocity calculation and theoretical sound velocity in pure water was 2.0%, and the relative error between sound pressure level calculation and theoretical sound propagation of spherical wave was about 6.0%. The experimental design deepens the understanding of abstract concepts such as sound pressure and sensitivity, and trains the students’ ability to use Excel for data processing.