Xinjing region is vast, where seismographic stations are sparse and the data of seismic wave velocity in the crust are few. So it is great difficult to determine the hypoeenters of the earthquakes. After repeated tests, we have selected a joint location method for joint determining the seismic wave velocity and hypoeenter parameters. Many computed results show that this method may improve the orientation error caused by unreasonable network arrangement. The computable wave velocity value is stable and the hypocentral parameters are reliable.