Based on the comprehensive model,the relation between v_P/v_S anomalous area evolution characteristics,positive or negative,before some moderate or strong earthquakes and main earthquake location in Gansu and its neighborhood is discussed by using convergent method.The results show that main shock often occurs on the boundary between negative and positive anomalous areas,as well as in the crossing area of different character velocity ratio anomalies.Moreover,it is discovered that there is a close relation between wave velocity ratio anomaly and the movement of adjustment element.The convergent method of wave velocity ratio spatial anomaly boundary has universal significance for predicting earthquake location.