Abstract: In order to measure moisture content of brown rice quickly，nondestructively and continuously，a microwave moisture detection device was designed.Effects of environmental factors and physical properties of brown rice on the accuracy of moisture detection were analyzed.Experimental results showed that ambient temperature，humidity and brown rice density had little influence on detection accuracy， with the increase of temperature，water activity of brown rice increased，and the microwave absorption ability increased，optimal detection thickness of sample pool was 50 mm，a moisture prediction model was established with brown rice temperature and microwave voltage as independent variables and brown rice moisture as dependent variables.It provided a technical reference for automatic treatment of rice wetting and roughening.