An unmanned aerial vehicle assisted task offloading and resource allocation method based on service caching is provided. The unmanned aerial vehicles are capable to cache a portion of programs to perform computation tasks for offloading of ground terminal devices, while a local terminal device is capable to cache a small number of programs. Under the constraints of task completion delay requirements for all devices and UAVs, as well as limited energy of UAVs, an optimization problem of minimizing the total time delay of request tasks of all ground terminal devices are established. This problem is a mixed integer nonlinear programming problem, which is decoupled into three sub-problems: task offloading decision, UAV resource allocation, and UAV trajectory. Slack variables, Lagrange multiplier method, and Taylor expansion method are used to iteratively solve the three sub-problems, and the optimal solutions for task offloading decision, UAV resource allocation, and UAV trajectory are obtained.