The invention discloses a terminal secure access method, device and system based on an electric power Internet of Things. The method comprises the following steps: receiving a first data request message sent by a terminal; acquiring hardware information of the terminal, and updating the first data request message according to a preset terminal address mapping table, a current gateway address and the hardware information to generate a second data request message; sending a second data request message; receiving terminal confirmation information fed back by the Internet of Things platform according to the second data request message; and accessing the terminal to the Internet of Things platform according to the terminal confirmation information. By implementing the method and the device, a data basis is provided for judging the legality of the terminal by the Internet of Things platform, and the terminal is accessed to the Internet of Things platform only when the terminal passes the verification of the Internet of Things platform, so that the secure access of the terminal is ensured, and the potential safety access hazard of the Internet of Things platform is eliminated.