The invention relates to a user access control method and system. The method comprises steps as follows: step S1, clients access a server; step S2, the server verifies information of the clients, operation in step S3 is performed if verification succeeds, otherwise, operation returns to the step S1; step S3, the server allocates an address and an access strategy corresponding to the address to each client based on a prebuilt IP address pool and the access strategy corresponding to each address in the address pool; step S4, the clients perform access according to the allocated addresses and the access strategies corresponding to the addresses. Different IP addresses can be allocated for the clients, and the clients are controlled to access private networks.