Studying dielectric properties of foods, not only can people understand radio frequency or microwave properties of foods, develop dielectric heating equipment which save most energy, but also can make dielectric properties be applied in evaluating food qualities. Therefore, permittivities of fruits and vegetables were introduced. The influences of test conditions, such as frequency and voltage of signal used in experiment, and environmental temperature and humidity on dielectric properties of fruits and vegetables were summarized. Progresses in studying dielectric properties influenced by qualities, such as water content, maturity, freshness, damage, total soluble solid content, etc., were reviewed. Problems existing in present research and development trends were also given.