To develop an intelligent granary management system (IGMS) based on Internet of Things (IOT), secure gateway of IOT (IOTGW), the key component in the system, is designed and achieved. According to the functional requirements of IOTGW in IGMS, embedded Web server is adopted as a lightweight approach for accessing perception devices and interacting with heterogeneous networks. The design scheme based on ARM chip and embedded Web server is given and the hardware and software architectures of IOTGW are investigated in detail. By comparing the major performances, AM3352, Linux, AppWeb, SQLite and C language are chosen for IOTGW implementation. In order to protect the sensitive information transmitted between the client and server, the secure sockets layer (SSL) protocol is added in AppWeb, and the compilation and transplantation of AppWeb with SSL are given detailedly. Experiment shows that the IOTGW can access different types of perception devices and actuators widely, exchange information between the perception layer and network layer safely, and control the perception nodes remotely, so the management of granary becomes convenient, efficient and intelligent.