The reasonable selection of interval tie line after network partition is of great significance to reducing the short circuit current, adjusting the power grid structure and avoiding the occurrence of cascading failures. Therefore, an evaluation method for the selection of interval tie line based on combinatorial weighting method of relative entropy is studied. The short circuit current, the power flow distribution, the flow transferring, the voltage stability, the node short circuit capacity are selected as the comprehensive evaluation indexes. And the overall short-circuit current level, the trend of entropy, the entropy of power flow transfer, the maximal load margin, the short circuit capacity margin are used to describe the above evaluation index quantitatively. To avoid the limitation of the single weighting method, combinatorial weighting method of relative entropy is used to determine weight for each evaluation index. Comprehensive assessment values of the selection of interval tie line schemes are obtained and optimal scheme is determined. Finally, the PSD power system analysis software is used to carry out the simulation. The effectiveness and feasibility of the proposed method are verified by the simulation example. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 2016YF-32).