Abstract: Based on the fundamental theory of tripotential sonde, the paper explained the principle, working method, the process of data processing of high density measurement method of electrical resistivity, and applied it to actual engineering. Through examples of analysis, Wenner array has obvious effect for detecting the up and down situation of bedrock surface due to its high vertical resolution. In addition, Wenner array has advantage of strong signal acquisition and high signal-to-noise ratio. Instead, dipole array has high sensitivity for detecting the internal structure of the bedrock due to its high transverse resolution. While dipole devise also has weak capability on signal acquisition and low ability of anti-jamming. To sum up, the paper concluded that it should get an ideal detecting results by combination. The actual application indicated that this method can get good result of detecting bedrock. It is proved by practice that the application of high density resistivity method in bedrock investigation can get great result. Furthermore; it would do great help to improve the exploration results and accuracy by combining different arrays for comprehensive measurement.