The present invention relates to a system for treating sewerage overflow, and more particularly, to a system for treating sewerage overflow, which goes beyond an existing method of treating combined sewerage overflow (CSO) only to a specific capacity and releasing same, regardless of water quality, without notice when a flow volume exceeds the specific capacity, and measures the water quality of the sewerage overflow by using the apparatus for automatically measuring water quality, so as to release over-capacity overflow when the water quality is fair, but treating the overflow by using a surfactant micro bubble floatation device comprising a surfactant micro bubble floatation treating tub when the water quality of the overflow does not meet a standard, thereby increasing efficiency in treating a non-point pollution source and significantly improving management efficiency as well. The system for treating the sewerage overflow, according to the present invention, comprises: the apparatus for automatically measuring the water quality of the sewerage overflow; the surfactant micro bubble floatation treatment device comprising the surfactant micro bubble floatation treatment tub for treating the sewerage overflow; and the controller for releasing the overflow when a measurement value of the apparatus for automatically measuring water quality satisfies a base value, and transferring the overflow to the surfactant micro bubble floatation treatment device when the measurement value does not satisfy the standard value.