In view of path planning problem of multiple unmanned aerial vehicle (UAV) hedgehopping penetration, it can be simplified to only consider UAV lateral movement level route planning. In the analysis of route planning constraints and under the problem assumption, the theorem of geometric shortest path was proved, focused on single threat situation, considering minimum turning radius and attack angle constraints, the shortest route of target attacking and the navigation point was calculated. route elusion and adjustment for sudden threat were discussed. Under the threat circles overlap cases, navigation coordinate deduction was studied. For route planning problem of multiple threats, a new trajectory planning geometric algorithm was proposed by the shortest tangent recursion method for avoidance of multiple threat circles. The simulation results verify rationality and validity of the new algorithm.