This paper designs an embedded 3G gateway that closely combines sensor technology, embedded technology and 3G technology. The gateway based on ARM9 processor takes embedded Linux 2.6 as the real time operation system. In this design, data from short-range wireless sensor network will be collected and aggregated after sensing and then sent to the control terminals through 3G mobile communication network through the gateway. The main contribution of this paper is that heterogeneous wireless sensor network merging, 3G longdistance data transmission and multi-terminal supporting are realized to serve the prosperous applications of Internet of Things.