CaCu₃Ti₄O₁₂ (CCTO) ceramic possesses high dielectric constant, and study of doping effects on the structure and properties is beneficial for the interpretation and optimization of dielectric properties of CCTO. In this work, we investigated the structure of CaCu₃Ti_3.95Zr_0.05O₁₂(CCTZ) ceramic by X-ray diffraction (XRD) and the properties of dielectric constant, relaxation, impedance, electric modulus at various temperatures with a dielectric analyzer in a broad range of frequency. The XRD results shows that Zr ions with 5% content can absolutely entered the CCTO crystal lattice. The analysis of impedance spectra and electric modulus suggested a close relationship between the electrical properties of grain and grain boundary and dielectric relaxations at low and high temperatures. Zr doping resulted in a large increase of activation energy of grain, while that for grain boundary was almost unchanged.