Moisture　content　is　the　most　direct　and　necessary　index　to　analyze　and　judge　agricultural　drought,　realize　water-saving　irrigation　and　hydrological　forecast.　In　order　to　grasp　the　information　of　soil　moisture　content　in　time　and　accurately,　a　soil　moisture　monitoring　system　based　on　narrow　band　internet　of　things　(NB-IoT)　was　designed.　Circular　cylinder　was　adopted　by　the　probe　of　the　system.　The　moisture　content　of　soil　was　measured　by　the　output　frequency　of　the　frequency　divider　in　the　probe,　and　the　capacitive　soil　moisture　sensor　was　calibrated.　The　calibration　experiment　of　the　sensor　showed　that　the　calibration　curve　adopted　the　cubic　polynomial　curve　of　the　output　frequency　of　the　sensor,　and　the　correlation　was　good,　and　the　determination　coefficient　can　reach　0.985　1.　The　influence　of　environmental　temperature　change　on　the　measurement　accuracy　of　soil　moisture　content　was　analyzed　with　a　thermostat,　and　the　temperature　change　of　1　and　the　frequency　division　of　the　probe　was　0.138　6　kHz,　a　first　order　linear　equation　was　obtained　to　compensate　the　influence　of　ambient　temperature　on　the　frequency　output　of　the　sensor.　Soil　moisture　content　was　measured　at　50.4~65.5　and　-18.0~23.6.　The　results　show　that　the　system　can　run　stably　and　reliably　at　high　temperature　and　low　temperature.　©　2019,　Chinese　Society　of　Agricultural　Machinery.　All　right　reserved.