In order to realize the online detection of micro solid targets in liquid, a new scheme of detecting micro solid targets in liquid based on RHC-7 hydrophone acquisition system was designed in this work. The bottle body produced the reverberation sound wave with the method of pulse excitation in detection system, which was collected and amplified by UTC1250VA amplifier system. The time-frequency analysis of the acoustic signal was carried out with the method of Mallat multiresolution, then the weak target signal was separated and extracted. The detected solid target influenced the spectrum distribution due to the viscous sound absorption and scattering sound absorption, then the correlation between detection signal and the reference signal was calculated to determine the detection threshold, which was an effective method to identify solid target in liquid. The experimental results show that the acoustic detection system is not only simple and practical, but also can detect the certain scale of target of the suspension and precipitation in liquid.