The invention discloses an online centralized monitoring system for distributed power distribution rooms, comprising a control device, a detection device, a video device, a field bus, a principal computer, a transmission device and a centralized monitoring device. The detection device and the control device are connected with the principal computer through the field bus. The principal computer and the video device are connected with the transmission device. The transmission device is in signal connection with the centralized monitoring device. The centralized monitoring device comprises a cloud server, an SCADA server, a GIS server and a video server. The centralized monitoring device integrates received data information of the SCADA server and the video server with geographic information in the GIS server, outputs geographic location information, topographic map, electric parameters, operation condition, environment parameters and intuitive video information of distributed power distribution rooms, and performs organic integration so as to achieve all-round monitoring on the power distribution rooms. The cloud server cloud-stores all the information and applies the information to cloud sharing, multi-terminal control, data backup, and other network applications. Thus, the system is made networked and intelligent.