A method for generating and using a virtual numb based on a SIM card and a secure communication system are provided, the generating method of the virtual number comprises the following steps: S1, generating the constraint requirements of the virtual number on the mobile phone APP of the user A, including: selecting the validity period of the virtual number, determining the service type of the userB and generating the key index and the parameter index by the mobile phone APP of the user A; S2, the mobile phone APP of the us A sends the constraint req of the virtual number to the SIM card A; S3, the SIM card A generates a virtual number representing the user A according to the constraint requirement and the real number of the user A; S4, the SIM card A returns the virtual number to the mobile phone APP of the user A. In the application, the user A actively generates a virtual number to share with the user B, and the user B uses the virtual number to make a call to the user A to preventthe real number of the user A from being disclosed, and the user B does not need to connect to the Internet to generate the virtual number before each call, so as to reduce the pressure on the operator platform.