The isothermal section of the Zr-Cr-Cu ternary system at 700 ℃ was investigated by using X-ray diffraction, scanning electron microscope and energy dispersive analysis. It was composed of 10 single-phase regions, 18 two-phase regions and 9 three-phase regions. The τ phase was observed to occur as a stable ternary phase at 700 ℃ when Cr was introduced. No ternary compound was observed in the Zr-rich corner and Cu-rich corner. The alloys in Zr-rich corner was consists of ZrCr2, (α-Zr) and CuZr2, while those in the Cu-rich corner was consists of (Cr), (Cu) and Cu5Zr.