Chemical conversion treatment on as-cast Zr-Al alloy was studied. After degreasing, pickling and chemical conversion treatment, a zinc chemical conversion film was fabricated on the surface of Zr-Al alloy. The microstructure and the phase composition of Zr-Al alloy and the chemical conversion film were observed using SEM and XRD, respectively. The results show that as-cast Zr-Al alloy is composed of α-Zr and Zr2Al, where α-Zr is substrate and Zr2Al spreads along grain boundaries discontinuously. A Zn3(PO4)2·H2O and ZnZr(PO4)2·2H2O chemical conversion film is formed by treatment in the chemical conversion solution successfully. The film consists of small crystal particles densely. It is uniform, compact and has no obvious defects. The forming mechanism of zinc chemical conversion film on Zr-Al alloy was discussed.