Texture evolution and superplastic deformation behavior of a quasi-single phase Zn-0.3wt%Al have been investigated. It was attempted to produce a stable and fine-grained microstructure in a dilute Zn-Al alloy through a proper thermomechanical treatment process (TMTP). The grain size of about 1 µm was obtained in the Zn-0.3 wt.% Al alloy and a relatively coarse grain size of 10 µm was also obtained through a subsequent aging treatment. The fine-grained material showed typical rolling texture with basal poles tilted about 30 degrees away from the ND toward RD, while the coarse-grained material showed a typical recrystallization texture with basal poles parallel to ND. A series of load relaxation and tensile tests were conducted at room temperature. According to the internal variable theory of structural superplasticity, the grain boundary characters of fine and coarse-grained materials were different from each other. A large elongation of about 1400% was obtained in fine-grained material at room temperature.