The invention belongs to the field of intelligent equipment for power systems, and particularly relates to a real-time online monitoring system for power distribution networks. The real-time online monitoring system comprises a CPU (central processing unit), an insulation monitoring module, a temperature acquisition module, an analog acquisition module, a switch input and output module and a communication unit. Data can be acquired by the insulation monitoring module, the temperature acquisition module, the analog acquisition module and the switch input and output module, and received data are classified according to priority levels by the CPU and are sequentially rated by the aid of high-grade tags, middle-grade tags and low-grade tags; the high-grade data, the middle-grade data and the low-grade data are distributed to a GPRS (general packet radio service) remote wireless module, a ZigBee-based local wireless module and a USB (universal serial bus) storage module via the communication unit to be classified and transmitted. The real-time online monitoring system has the advantages that the real-time online monitoring system is provided with a communication module with a combination of double wireless communication systems and USB communication, accordingly, problems of data jamming and high communication expenses can be solved, large quantities of data of the power distribution networks can be provided for operating personnel, and devices can effectively adapt to actual engineering conditions.