Hemihydrate calcium sulfate whiske were prepared from phosphogypsum, which is phosphate mining enterprises produce waste slag, by raditional normal pressure alcohol hydrothermal method adding CaSO4 · 2H2O as crystal seed. In order to find the optimum preparation conditions, the effects of seed content, glycerol content and phosphogypsum mass fraction on the structure and morphology of whiskers were investigated by single factor test. These samples were characterized by SEM and XRD. The results show that the aspect ratio of the whisker prepared with CaSO4·2H2O crystal seed (49.29) is 30.99, which is about 60% higher than that prepared with glycerol. When the volume ratio (V) of glycerol to water is 1, the content of seed is 1%, and the mass fraction of phosphogypsum is 5%, the average diameter of prepared whiskers is 0.65 μm, the aspect ratio is 62.15, and the size of whiskers is uniform. These results indicate that hemihydrate calcium sulfate whisker with high aspect ratio and uniform size can be prepared by adding 1%CaSO4·2H2O seed, glycerol with V of 1 and phosphogypsum with mass fraction of 5% under atmospheric pressure.