Abstract: A simultaneous travel time inversion procedure was developed in collaboration with a modified shortest path algorithm, which was applied to a bent ray tracing forward calculation. The conjugate gradient algorithm was used to solve a damped least square problem. The crustal P-wave velocity structure beneath the Loess Plateau and its surrounding regions of China were tomographically imagined down to the depth of 50 km by inverting P wave travel time data from local and regional earthquakes. The result indicates that lateral high velocity anomaly regions generally coincide with the seismically active zones, while vertical velocity variations show existence of a low velocity zone.