The invention relates to a method of identifying user identity by a digital certificate based on a separating mapping network, which adopts an IP address as a routing address and constructs an access address by the digital certificate. The method comprises the following steps: firstly acquiring the digital certificate from a certification authority when a user accesses to a network; then using the digital certificate to confirm the user true identity so as to prevent an illegal user accessing to the network; and when carrying out mutual communication among communication terminals, confirmingrespective identity information by using the digital certificate. The invention introduces a system of using the digital certificate to confirm the user identity aiming at an address separating mapping network, and realizes the true identity identification of an access terminal and the mutual true identity identification between communication parties, thereby preventing the illegal user accessingto the network, standardizing the user network behavior and providing a safe network environment for the user.