A new method for studying the seismic velocity ratio anomalies was proposed. Its characteristics are:1). in the normal case the velocity ratio is a constant; 2). the anomalies are more obvious; 3). the data are added as many as possible, including those of earthquakes occurred in the boundary of the anomalous velocity ratio region, so that the information of the earthquake preparatory region can be provided in time. When the method is adopted to check the earthquake preparatory region in Gansu Province, better results have been obtained.