Method and system for network access control based on NAT

The invention discloses a method and a system controlling the network access based on the network address conversion. The network system comprises a gateway and a network packet processing unit. The method comprises the following steps that: the gateway receives a network packet sent by a first device and the network packet has a target address corresponding to a second device; the gateway carriesout the network address conversion of the network packet, converts the target address of the network packet into the address corresponding to the network packet processing unit and sends the networkpacket to the network processing unit; the network packet processing unit processes the network packet and sends the processed network packet back to the gateway; the gateway carries out the network address conversion of the network packet and converts the target address of the network packet into the target address corresponding to the second device and sends the network packet to the second device. As the network packet is transmitted to the network packet processing unit to be correspondingly processed, the working task of the gateway can be shared so as to ensure the processing progress ofthe gateway and enhance the system performance.