The effect of thermal cycle frequency on the transformation superplasticity of Zn-Al cast alloy containing alumni with a fraction of 5 percent was investigated with the constant load creep test. The results show that under the condition of thermal cycle tension test at 20 ～ 350℃, the tensile elongation percentage of the Zn-Al cast alloy can exceed 100 percent, and the alloy exhibits transformation superplasticity clearly. The thermal cycle frequency has an obvious effect on the transformation superplasticity of Zn-Al alloy. When the thermal cycle temperature range and external load keep constant, the superplastic elongation percentage will increase, while the strain rate in the quasi-steady deformation state will decrease with increasing thermal cycle frequency. The transformation superplasticity of Zn-Al alloy is related to the characteristics of the interphase boundaries between new and origin phases in the eutectoid transition region. In the thermal cycle phase transition process, Newton viscous flow of Zn-Al alloy occured in the interphase boundaries between new and origin phases. The diffusion of atoms between the interphase boundaries had a coordinated effect on the deformation of Zn-Al alloy in the thermal cycle process.