The invention discloses a satellite task planning method with the minimum completion time under the condition of sufficient resources, and the method comprises the steps: 1, carrying out the discretization representation of a to-be-observed region through a grid, and enabling an original coverage problem of a larger region to be converted into a coverage problem of the grid; 2, obtaining a feasible solution on the coarse-grained grid and then cutting down the feasible solution, and finding a better feasible solution on the fine-grained grid; 3, repeatedly refining the grid in a nesting manner,and proposing a method for constructing a near coverage mode on the new grid to prevent all coverage modes from being regenerated each time; and 4, combining grid refinement, construction of a near coverage mode and a dynamic greedy-based heuristic algorithm, and performing multiple iterations to obtain a better feasible solution. According to the method, the satellite task arrangement result taking the minimum completion time as the purpose can be quickly obtained, so that the satellite can finish the observation task as early as possible under sufficient observation resources, the time required for executing the task is shortened, and the working efficiency of the satellite is improved.