Based on the current situation of the river blocking structures in the Songhua River basin, the barrier coefficient method is used to evaluate the longitudinal connectivity of the main tributaries. The results show that the longitudinal connectivity indices of the Songhua River and Nenjiang are 0. 21 and 0. 27 respectively, the connectivity grade is good. The connectivity index of the second Songhua River is 0. 62, and the connectivity level is medium. The best connectivity among the Nenjiang tributaries is Nenjiang, which is the only passageway for cold water fish to interflow with the lower reaches of Nierji, Nenjiang. The connectivity of the Gan River, Yalu River, Chuoer River and Nemo River connectivity level is good, and the same of the Taoer River, Huolin River and Wu Yuer River is inferior. Yitong River and Yinma River of the second Songhua River tributary have numerous dams, fish migration is blocked, their connectivity level is inferior. Mudanjiang, Lalin River of Songhua River tributaries are influenced by the development of cascade hydropower stations, their evaluation index is bad; Wukan River, Tangwang River, affected by the construction of dam gates, reservoirs and hydropower stations along the river irrigation area, evaluation grade for them is poor. At present, the endangered rare fish in these tributaries have been extinct, cold water fish are rarely seen. Fish pass structures are not built in the whole basin, which blocks fish migration and population exchange. Such measures as to make up and build fish pass structures and carry out the proliferation and release of fish if necessary are proposed in this paper. The river structures without reserved ecological flow are to be reconstructed or the ecological flow is discharged by using the existing facilities. For those river structures with reserved ecological flow, reservoir regulation scheme shall be adjusted to ensure that the discharged volume will meet fish survival needs at different times and in different spaces.