Firewall, VPN (virtual private network) and NAT (network address translation) are traditional network security technologies and each has different function. But some network security systems cannot combine these technologies, cannot give attention to efficiency of system, and scarce of fine-granularity inner security management. In order to solve these problems, an integrated and scalable network security system, NEUSec (NEUsoft security system), is presented in this paper, which integrates packet-filter, VPN and NAT technologies(NEUsoft security systenm),is presented in this paper,which integrates packet-filter,VPN and NAT technologies under Linux environment,combines NAT and proxy technogies to construct scalable virtual proxy server,the radix-based security policy search mechanism is presented,and the RBAC(role-based access control)technology is inrtod to solve inner security management.Compared with other security systems,NEUSes,is an all-around and scalable security system and gives an attention to efficency.It has achieved a satisfactory result in practice.