The invention relates to an online monitoring system for the microclimate of an intelligent substation, which comprises a foundation layer, a fence, a monitoring device, a concentrator and a monitoring center, and is characterized in that the monitoring device is arranged on the foundation layer, the concentrator is connected with the monitoring device, the monitoring center is connected with theconcentrator, and the monitoring center is connected to a warning device. The online monitoring system has the advantages that variation conditions of the microclimate in the substation are monitoredand collected in real time through the monitoring device, the monitored and collected data is transmitted to the monitoring center through the concentrator, the monitoring center stores the data and achieves release and checking for the data via a browser through a PC of the monitoring center, variation conditions of the microclimate of each substation can be checked in real time through the browser, a short message alarm notice is sent to an operation watchkeeper within the shortest time when out-of-limit data occurs through the setting of the warning device, timeliness and accuracy are achieved, and safe running of the substation in bad weather conditions are ensured.