Based on[1] [2], imaging of seismic velocity structure of crust and upper mantle for the northern portion of N-S Seismic Belt is made. The velocity distribution of upper crust exists three low-velocity belts oriented near EW trend, which agrees with recent active fracturing zones, while in upper mante there are a lot of low velocity belts trend NE and NW, which appear network structures across each other. It is pointed out that the Haiyuan-Guyuan fracturing zone may be a great deep fault, being low velocity belts in upper-, lower-crust and upper mantle. Finally, it is suggested that the northeastern boundary of the Qinghai-Xizhang Block may locate along Tianzhu-Lanzhou-Jingning-Qianyang-Lueyang-Jiangyou, by using inversion.