The northern piedmont fault of Xizhou Mountain is the seismogenic structure of the Dingxiang M7 earthquake in 1038. It may have one or more secondary faults in the basin, which may be very near Xinzhou city. This study uses the microtremor method to detect whether hidden secondary faults exist in the northern piedmont fault of Xizhou Mountain. The locations of approximately 17 remarkable breakpoints were obtained through the lateral change in resonance frequency and the relationship between bedrock depth and frequency. The results indicate that three obvious secondary faults exist in front of Xizhou Mountain, as well as the location of their breakpoints, relative offset, and corresponding strike distribution. This research provides basic data for earthquake prevention and disaster reduction in Xinzhou city.