CaCu3Ti4O12(CCTO), SrCu3Ti4O12(SCTO) and BaCu3Ti4O12(BCTO) ceramics with ideal molar ratio were prepared by the traditional solid-state reaction method. The temperature dependence of dielectric constant and dielectric loss at different frequencies for the samples were measured. It is found that the dielectric properties of CaCu3Ti4O12 are attributed to Debye relaxation theory, while the great difference of the dielectric properties between SCTO, BCTO and CCTO comes from the aberrance of structure and the appearance of impurity