When the aircraft needs to change the path temporarily in case of emergencies during navigation, the efficiency and reliability of the route planning algorithm are urgently required. An improved Dijkstra algorithm with pre search is proposed to solve this problem. A more objective track evaluation function is established by using the normalized entropy weight method to simplify the multi-objective track optimization model. The backtracking function of D algorithm is realized by adding the pre search process with depth of one, which solves the problem of high failure rate of path search under complex constraints due to insufficient relaxation of classical D algorithm. In addition, a break mechanism is added in the pre search traversal process to further reduce the operation time. Simulation results show that the operation time of the proposed algorithm is reduced by 46% compared with ordinary backtracking D algorithm. And the algorithm is close to intelligent algorithm in path search success rate and the accuracy of the shortest path decision under complex constraints, which can meet the requirements of fast path planning under complex conditions.