Crystal shape of phosphogypsum was controlled under simulated extraction reaction conditions of wet process phosphoric acid production. The crystal shape of phosphogypsum was observed using scanning electron microscopy, the crystal size distribution and average particle size were determined by laser particle size analyzer. The results show that the contents of free H2SO4 and P2O5 in liquid phase affect both crystal shape and crystal size. When the former increases, the crystallization supersaturation of dihydrate gypsum decreases; the crystal shape changes from thin sheet into thick cylinder and rhombic, then changes to polycrystal; the average crystal size becomes larger. When the latter increases, the crystallization supersaturation of dihydrate gypsum increases; the crystal shape changes from thick plate into thick columnar, then changes to thin needle; the average crystal size becomes smaller; when the reaction temperature increases, the crystallization supersaturation of dihydrate gypsum decreases; the average crystal size becomes larger, but the crystal shape is the same, which is cylinder. From the points of wet phosphoric acid production and utilization of phosphogypsum in building materials, the optimal extraction reaction conditions are proposed as follows:the content of free H2SO4 in liquid phase at 5%(by mass), the content of P2O5 in liquid phase at 15% to 20%(by mass), reaction temperature at about 80℃ and the liquid to solid ratio of slurry is 2.5∶1.