Underground mining easily causes casualties, and illegal mining is a major contributor to this issue. It is a challenge to locate and differentiate illegal mines from approved mines over a vast area. Over the past few years, our research in satellite differential radar interferometry (DInSAR) to monitor underground-mine-induced surface subsidence has demonstrated the reliability of DInSAR. In this paper, a DInSAR-based illegal-mining detection system (DIMDS) is proposed to exploit the geometric, spatial, and temporal characteristics of those subsidence patterns. Testing results over a coalfield in Asia have proven the efficiency, reliability, and cost effectiveness of DIMDS in finding out illegal mines.