The invention provides a security authentication system and method for a smart power terminal. The system comprises a security detection server, a power server, an online monitoring server and an address registration server. The method comprises the following steps that: firstly, the address registration server performs uniqueness detection on the terminal, and generates a registration serial number and transmits the generated registration serial number to the security detection server if the terminal is legal; the security detection server judges whether terminal key object information is matched with power service permission allocation request information of the terminal or not, and generates unique terminal identity authentication information; and the terminal performs authentication and registration on the power server to obtain corresponding services. The system and the method provided by the invention are flexible and effective. Reliable authentication of software is realized without hardware authentication. Meanwhile, the terminal identity authentication information is protected from being stolen. A security detection method which is more efficient and economical than an existing hardware authentication method is provided for the power terminal, so that secure and efficient running of a smart power grid into which an Internet technology is introduced is ensured.