Abstract: The oil shale old goaf in Zhaozhuang Village of Luanchuan County has posed a certain threat to the local living environment. However, this goaf has small scale, complex distribution, and interference from crowded people, which made it difficult for detection. In order to detect the goaf effectively, the authors in this paper proposed a combined detection method of microtremor survey and high-density electrical method. The two-dimensional apparent velocity and resistivity profiles were obtained through data acquisition and processing. Then, the oil shale rich layer was identified as medium resistivity layer with approximate layered distribution in the resistivity profile, and the oil shale goaf was identified as low velocity anomaly area in the horizontal direction of medium resistivity layer, according to the actual geological condition. The verified results from drilling indicate the inference results of the combination method are basically consistent with the reality, which prove the combination method is feasible for the exploration of small-scale ancient goaf of oil shale, with strong anti-interference features and high-efficiency construction.