A method and system are provided for detecting conflicts between a power supply guarantee request (PSGR) and an outage request (OR) in a power grid. The system comprises: an accompanying outage analysis device for receiving a first outage device set including OR related devices, and using geographic information about devices in the power grid to determine a second outage device set, the second outage device set including devices in the first outage device set and accompanying outage devices that need to be in outage together with the devices in the first outage device set; an outage scale determination device for using topology information about the power grid to determine a power grid outage scale in which all of the devices in the second outage device set can be in outage; and a conflict detection device for receiving a power supply guarantee device set including PSGR related devices, and judging, for each device in the power supply guarantee device set, whether the device is included in the power grid outage scale.