The invention discloses a low-voltage power distribution Internet of Things system and a device plug-and-play method. The system comprises a cloud master station, an intelligent distribution transformer terminal, a low-voltage device and a communication channel. The cloud master station comprises an IOT platform and a master station application service module, and the IOT platform performs application registration on the master station application service module, so that the master station is connected to the low-voltage equipment in a plug-and-play manner; the intelligent distribution transformer terminal comprises an HPLC head end and a plug-and-play APP. The plug-and-play APP communicates with the HPLC head end, reads the node information and the address information, communicates with the low-voltage equipment according to the obtained address information, reads and stores the equipment information, generates an equipment online notification according to the equipment information, and sends the equipment online notification to an IOT platform of the cloud master station; the low-voltage equipment comprises an equipment body and an HPLC module, and node information of the equipment body is sent to the HPLC head end of the intelligent distribution transformer terminal through the HPLC module of the low-voltage equipment. According to the invention, the intelligent distributiontransformer terminal is used as a calculation core, and the fine management level of the distribution area and the equipment access debugging efficiency are improved.