This paper designs and implements an embedded security gateway based on double-homed structure which composed of software and hardware parts. The core of hardware platform is based on two S3C6410 processors and one EP1C18F4620 FPGA. The software is based on reduced Linux kernel 3.0.1. The gateway uses Net-filter/IP-tables firewall, IPSec VPN and Network isolation technologies. And it can effectively reduce the risk of transmitting information by public network and improve the defensive capability. So it can be applied to the business with high security level.