The distribution network is a crucial and highly effective component in the construction of the ubiquitous power Internet of Things (IoT). To enhance the construction, operation, and maintenance levels of the distribution network, research on online monitoring technology for the integration of primary and secondary in IoT ring main units is conducted. Starting from national industrial policies and through comparative analysis of domestic and international technologies, this paper mainly introduces the design and implementation of an online monitoring solution in IoT ring main units based on high-precision sensing technology. This includes functions such as wireless temperature measurement, temperature and humidity monitoring, smoke and fire detection, water immersion detection, mechanical characteristic monitoring, and partial discharge monitoring. Practice has shown that this design achieves real-time temperature monitoring of cable plugs, providing early warnings for overheating caused by cable connection anomalies and discharges, thereby effectively reducing the impact range of faults. Using UHF technology, it realizes online monitoring of partial discharges, promptly detecting discharge situations in primary switches for maintenance, which is of great significance for the stable operation of switches.