Considering the increasing demand for data collection in ocean, forestry, meteorology and water conservancy, we proposed a kind of satellite Internet of Things system level solution based on TT-1 satellite mobile communication system which is working well. This paper studies the satellite IoT system architecture and the transformation of the TT-1 air interface, including the physical layer design, access design of terminal and improvement of communication protocol, etc. Therefore, a brand-new kind of system which can run both the normal operation of TT-1 system and the efficient data collection business is built. The preliminary test results in the Bureau of Meteorology and Hydrology show that this IoT system based on TT-1 designed in this paper can meet the needs of information collection in the field of meteorology and hydrology.