The invention discloses a safety and stability online prevention and control optimization decision method for multi-stage scheduling collaboration of a power grid, and belongs to the technical field of power system scheduling operation control. Due to the fact that safety and stability problems in a large power grid are interwoven with each other, an operation control mode of a multi-stage regulation and control method is combined so as to disclose an online operation mode and prevention and control candidate measures for a power grid, which comprises the regulation and control center and a direct subordinate regulation and control center thereof, a direct superior regulation and control center and a direct subordinate regulation and control center thereof, at each regulation and control center at each stage, so that safety and stability online estimation on a fault set which directly defenses the large power grid is carried out; influencing factors of cooperative defense of the regulation and control center at each stage are introduced to compute control performance comprehensive indexes of prevention and control candidate measures, so that prevention and control measure calculation for the fault set which directly defenses the large power grid is carried out; and safety and stability verification is carried out on the combined prevention and control measures, so that the safety and stability online prevention and control optimization decision method for multi-stage scheduling collaboration can be realized.