The invention provides an active distribution network multi-time scale optimization method considering source-grid-load coordination interaction. The method comprises the following steps: (1) in view of a given distribution network with a distributed power supply, in combination of weather information, next-day 24h load prediction and distributed power supply output prediction are carried out; (2) in consideration of constraints of switching operation times, time partitioning is carried out on a next-day 24h load curve; (3) according to a load curve partitioning result, day-ahead multi-time period source-grid coordination optimization is carried out; (4) based on a day-ahead power grid scheduling plan and distributed power supply output arrangement, daily flexible load optimization scheduling is carried out; and (5) through the source-grid coordination optimization and the flexible load optimization scheduling, the distributed power supply and various flexible loads are made full use of, and source-grid-load real-time power balance is achieved. Reasonable power flow distribution is realized, the grid loss can be effectively reduced, the node voltage level and the power quality are enhanced, and the economy and the reliability of power grid operation are enhanced.