In order to study the attenuation characteristics of elastic wave, ultrasonic sensors are used to monitor wave propagating variation in medium-grained sandstone by the combined method of frequency spectral conversion, mathematical statistics and curve fitting. The results show that, after analog-digital conversion and filtering, the frequency of elastic wave is between 100~500 kHz, and the amplitude obviously decreases as the propagation distance increases in both frequency and time domain, and the high frequency components are attenuated more seriously than the low frequency components. Centroid frequency linearly decreases with the increasing propagating distance, and it shows more signal messages with stable variation than the main frequency. The attenuation coefficient in the sandstone acquired by waveform comparison method is 0.016 dB/cm. In the lab dimension, as the propagating distance increases, absolute energy decreases following a law of negative exponential change, and amplitude and ring counts stably decrease as linear trend, but the rise time trends to increase. Understanding the attenuation characteristics and sensitive degree of elastic wave is meaningful for inversing failure source characteristics in microseism monitoring and acoustic emission experiments.