In obtaining the travel time of sound/time difference in ultrasonic measurements, locating the ultrasonic wave head is pivotal. The existing location/detection methods are poor in terms of accuracy and anti-jamming capability. Therefore, they cannot be used in certain high precision fields. Hence, this study develops a novel method based on spectrum-subtracted sub-band singular spectrum entropy (SSB-SSE), which locates the wave head by introducing both sub-band and spectrum subtraction into singular spectrum entropy (SSE). Furthermore, this study generates a reasonable sub-band selection technique. Simulation experiments demonstrate that SSB-SSE is more accurate, robust, and capable of anti-jamming than other existing spectrum entropies. Therefore it can locate ultrasonic wave heads more effectively in layered media measurements.