Abstract: CaCu₃Ti₄O₁₂ ceramics were fabricated by solidstate reaction method. The dielectric properties and internal friction were measured by impedance meter. The results show that the internal friction of CaCu₃Ti₄O₁₂ ceramics reaches its maximum at a certain temperature under a given frequency, and decreases rapidly when being offset from the temperature. On the other hand, there is a shift of internal friction to the high temperature region with the frequency increasing. A further study shows that the dielectric constant of the ceramics is smaller at a low temperature, but it suddenly changes at a certain temperature, then keeps the higher value with the increase of temperature. Meanwhile, the corresponding temperature for the sudden change increases with the frequency. The giant dielectric constant of CaCu₃Ti₄O₁₂ has some relation with the intrinsic structure and barrierlayer capacitance, and the mutual dependence relations between the internal friction, frequency and the temperature are adapted to the polarization model, in which the sudden change induced by the dielectric constant under a certain temperature is related to the characteristic of the polaron.