Presently, water solution mining serves as the primary method for extracting salt deposits; however, precise control over cavity development and spatial migration poses challenges. To determine the spatial location of cavity development during the extraction of water-soluble salt mines, this study utilizes 23 days of continuous waveform data collected by 169 short-period seismographs deployed in the Zhangshu Salt mining area of Jiangxi Province. Microtremor imaging and microseismic event detection and location are employed for this purpose. Microtremor imaging elucidated the velocity structure within an approximate area of 2 km², revealing the depth and morphology of the salt mine roof and the location of dissolved cavities. Throughout the instrument deployment period, four microseismic events were monitored, indicating relatively weak roof activity of the dissolved cavity. Comparison of microseismic event locations with the velocity structure obtained through microtremor imaging revealed that all events transpired at the salt mine roof and in low-velocity dissolved regions. The findings indicate that the integration of microtremor imaging and microseismic location is a viable approach for detecting salt mine cavities and studying roof activity. This method offers technical support in mitigating geological hazards and informs subsequent salt mine design and mining operations.