In order to offer a portable, quick and precise method and instrument for measuring moisture content of coarse cereals, a moisture meter was designed based on dielectric properties and C51 language. DC charge/discharge circuit, digital temperature sensor DS18B20 and equal-arm bridge circuit were used to detect the values of capacitance, temperature and bulk density of coarse cereals. Millet was used as sample to study the influence of moisture content, temperature and bulk density on capacitance with the self-made moisture meter. Mathematical model, describing their relationship, was regressed and verified. The accuracy in predicting moisture content from obtained capacitance and temperature was tested. The results showed that the measurement precision for moisture content was ±0.5% and the response time was less than 3s when the moisture content in wet basis was within 11%~19% and in temperature of 5~40℃.