A NAT method, apparatus and device are provided. According to the method, a target IP address and its reference port are obtained from a NAT resource pool, the reference port being a port in a corresponding consecutive port range. A first five-tuple is generated based on the target IP address, the reference port and an original five-tuple of the packet, and a second five-tuple is obtained by masking first-class bits of the reference port of the first five-tuple. Based on a hash result of the second five-tuple, a target bit indicating a non-conflicting state is determined from a pre-constructed bitmap. The state indicated by the target bit is set to be a conflicting state, and a target five-tuple is generated based on the target bit. The target five-tuple and the original five-tuple are recorded in a session table, and the packet is NAT-processed based on the target five-tuple.