The phase equilibria of the Cu-Co-Zn ternary system at 800°C and 1000°C were investigated by means of electron probe microanalysis and X-ray diffraction. No ternary compound was found. At 800°C, the solubility of Co in the β-CuZn, and Cu in the β1-CoZn at 800°C were 32.36 at.% and 5.28 at.%, respectively. The γ-Co5Zn21 and γ-Cu5Zn8 showed the same crystal structure, an infinite region of mutual solubility was observed in the Cu-Co-Zn ternary system. It was confirmed that as the temperature rises from 800°C to 1000°C, the liquid-phase region was further expanded. The isothermal section of 1000oC was simple. The phase of β-CuZn, β1-CoZn, γ-Co5Zn21 and γ-Cu5Zn8 was disappeared. The region of liquid phase is very large.