Phase equilibria of the Al-Cu-Zn system on Al-Zn rich side was experimentally determined with 16 alloys annealed at 360 °C. The annealed alloys were examined by means of x-ray diffraction, electron probe microanalysis and differential scanning calorimetry. Five single-phase regions and seven two-phase regions as well as three three-phase regions, i.e. α-(Al) + θ-Al2Cu + τ′-Al4Cu3Zn, α-(Al) + τ′-Al4Cu3Zn + ε-CuZn4 and α-(Al) + ε-CuZn4 + (Zn), were determined. The partial isothermal section of the Al-Cu-Zn system on Al-Zn rich side at 360 °C was constructed based on the obtained experimental data in this work. It was observed that the solid solution phase α-(Al) would easily decompose into ε-CuZn4, (Zn) and α′-(Al) at the ambient temperature in the early stages. The ternary phase τ′-Al4Cu3Zn would form and ε-CuZn4 would disappear gradually along with the extension of aging time.