Identifying the distribution of karst is an important task in bridge survey in karst areas of highways. In the past, only a combination of drilling and high-density electrical methods was used to basically determine the distribution of karst. However, due to the small influence surface of drilling, the accuracy of high-density electrical methods is not high, resulting in low accuracy of survey results. This article uses traditional drilling and high-density electrical survey methods to preliminarily determine the distribution of karst. After the pile foundation construction reaches the elevation of the pile bottom, the method of detecting karst at the pile bottom is combined. This can accurately detect the distribution of karst at the bottom of the pile. Through this method, the stability of the foundation pile after grouting can be ensured, thereby ensuring the safety of operation.