The invention discloses a method for staggered optimal dispatching of a cascade reservoir group. The method comprises the following steps of: 1, when the reservoir inflow of incoming water is smaller than the fully-loaded flow of upstream and downstream reservoirs in a cascade reservoir group, carrying out power generation on each reservoir according to the inflow, and if redundant water yield is predicted, increasing the output of each reservoir in advance until the reservoir is fully loaded; 2, when flood is forecasted, increasing the output power generation of each reservoir in advance, carrying out full-load operation on the upstream reservoirs to reduce the water levels of the reservoirs to a dead water level threshold value and then empty the reservoir capacity, and when flood happens, closing the upstream reservoirs so as to back up the flood for the downstream reservoirs under the premise that the downstream reservoirs are fully loaded; 3, if the water levels of the upstream reservoir power stations rises to exceed a normal high water level and heavy rainfall is forecasted in N days, operating the upstream reservoirs for flood discharge; and 4, after the water levels fall, opening the upstream reservoirs to ensure that the downstream reservoirs are fully-loaded. According to the method disclosed by the invention, cascade hydropower station centralized dispatching management is adopted, so that optimal dispatching is realized and the electric quantity is increased.