Various ceramics were prepared by the conventional solid-state reaction technique according to the compositional formula of (1-x) BaTiO3 + x CuO with x = 0.00 ~ 0.05. The influence of CuO additive on microstructure, crystalline structure and dielectric and piezoelectric properties were investigated. It has been found that CuO acts like a sintering aid in the CuO-modified BaTiO3 ceramics to promote the ceramic densification and suppress the abnormal grain growth during sintering process, and decreases the orthorhombic-tetragonal phase transition temperature. The CuO-modified BaTiO3 ceramics show desirable microstructures with high density, small average grain size and uniform grain size distribution. For the one with x = 0.01, it has the good piezoelectric properties of d33 = 300 pC/N, kp = 0.49, k33 = 0.62 and Qm = 425 at room temperature, and exhibits a ε' peak at -5°C and a d33 maximum of 353 pC/N at 0°C, respectively.