Applying the data of 7 artificial explosions we calculate the average crustal thickness and the average thinckness of the upper layer, and various seismic velicities in the area of southeast of Gansu, the north of Sichuan, the south of Shaanxi, the south of Ningxia and the northeast of Qinghai and the contiguous areas of Gansu, Sichuan, Shaanxi respectively. It is suggested that thickness on contiguous areas of Gansu, Sichuan and Shaanxi is quite close and the crustal thickness decreases from northwest to southeast gradually.