The invention belongs to the field of electric power information security, and relates to an RSA public key cryptography based off-line electric power transaction information system authorization method which is applied to remote off-line authorization. According to the method, a client applies for a remote authorization code from a server firstly, the server automatically generates authorization codes with high complexity and provides the authorization code for the client, the client selects one of the authorization codes and stores the authorization code, the authorization code is encrypted by using a private key of the client, all of the authorization codes are encrypted by using a public key of the server and provided for the server; and the server verifies authorization codes submitted by the client, stores all of the authorization codes after the verification is successful, and prompts that the application for the authorization code of the client is successful. The client can carry out remote authorization after receiving the authorization code, and the process of authorization is very simple. According to the method provided by the invention, encrypted transmission for the authorization codes is carried out by adopting an RSA public key method, so that the security of the method is based on an RSA public key system, and security requirements of an electric power information system can be achieved.