An on-line resistance-type moisture sensor adopted by circulating dryer was developed by the domestic manufacturer under the cooperative project. The mechanisms of the sensing systems were modified to solve the sampling problems. The relationships between moisture contents of grains and its conductance was established for local rice varieties. Comparing the moisture contents determined from the sensors with those from the standard oven drying method, the deviations was within 1.0% under the measuring range from 20 to 12% w.b.. These sensors have been commercialized.