Pearl barley was used to study the influence of frequency (1~1000kHz), temperature (5~40℃) and moisture content (14.7%~22.7%) on the relative dielectric constant. The reasons for dielectric constant changed with these factors were analyzed. Furthermore, the mathematical model for predicating moisture content of pearl barley based on the dielectric constant and temperature at 100kHz was established, and the model was verified. The results indicated that the dielectric constant of pearl barley increased as moisture content and temperature increasing, decreased with frequency increasing over the frequency range from 1~1000kHz. The relationship between the dielectric constant, temperature and moisture content can be described by cubic polynomial, with the coefficient of determination of 0.9976 at 100kHz. Obvious linear relationship was observed between measured moisture contents and calculated moisture contents, with coefficient of determination of 0.9977.