The invention discloses an out-of-step separation control method and system based on the wide area information, and a readable storage medium. The method comprises steps that the real-time power information monitored by power monitoring devices in a power monitoring device group is received; the power information is integrated and classified according to types of the power monitoring devices; theintegrated and classified power information is transmitted to a central server, and an out-of-step type of a current power system is determined by the central server based on the power information; the control strategy of the current power system is determined according to the out-of-step type, and corresponding control behaviors are performed according to the control strategy. A power system in the prior art often fails to operate after 2-3 oscillation cycles after a system out-of-step, when an out-of-step oscillation section is composed of multiple transmission channels, the judgment time ofthe channels is inconsistent, a problem of aggravated loss due to collapse of the power system as the final separation time of the section depends on the separation time of the latest separated transmission channel is generated, and the problem is solved through the method.