The dielectric properties of tilapia at different parts (anterior, middle, tails, belly), different temperatures (10~90 °C), different frequencies (300~3 000 MHz ), and different moisture contents (3.8590~ 0.1161 g/g d.b. (dry basis)) were determined using the coaxial line method. The dielectric constants of tilapia among four parts were similar, the greatest difference was 4.91, and the average difference was 2.37. Four parts of tilapia were the same in variation trend of dielectric loss, but the value of belly was lower than that of others. This is perhaps the fact that It is maybe the fat content of belly was higher than other parts. However, due to the differences were small, the effects of components on dielectric loss can be ignored. For this reason, the average of dielectric properties values(ε^?, ε^?) for four parts were employed to investigate the effect of temperature, frequency, moisture content on tilapia dielectric properties valuse (ε^?, ε^?). In addition, the dielectric constant of tilapia decreased with the increase of frequency and temperature, and decreased along with the decrease of moisture content. However, with the increase of frequency, the dielectric loss decreased to a minimum (2 300 MHz) and then increased. When the frequency was lower than 2 300 MHz, dielectric loss increased as the temperature increased, and when the frequency was higher than 2 300 MHz, it was contrary. The dielectric loss also decreased with the decrease of moisture content. Moreover, the penetration depth[Frequency: 915, 2 450 MHz; Temperature: 10-90 °C; Moisture content: 3.8590-0.1161 g/g d.b. (dry basis)] of tilapia was calculated, regression analysis was employed to develop polynomial equations of dielectric properties and penetration depth. The predicted values and the experimental values were well correlated.