The amplitude of ultrasonic wave is attenuated in propagation, and the attenuation is related to the distance of propagation and the center frequency of ultrasonic transducer. In order to study the frequency effect of high-frequency ultrasonic attenuation, this paper analyzes the amplitude and spectral variation of pulsed ultrasonic wave reflection in water by pulse echo method, and studies the relationships between the amplitude attenuation and the propagation distance of ultrasonic wave in water as well as its ultrasonic frequency. The reflected echoes at different distances are collected, and the echoes are subjected to Fourier transform to analyze the distance effect and frequency effect of ultrasonic propagation attenuation. It is found that the propagation attenuation of ultrasonic waves in water is exponential with distance, and the attenuation coefficients of ultrasonic waves of different frequencies are different. The higher the frequency, the greater the attenuation. The frequency effect of attenuation can effectively explain that the center frequency of the echo pulse signal is much lower than the nominal center frequency of the transducer in high-frequency pulse ultrasonic detection by reflection method.