Anhydrite powders with nanostructure surface were prepared in Ca(OH)2-H2O-CO2 system. The effects of preparation parameters such as Ca(OH)2 concentration, revolution speed of mixer, temperature on surface finish and reaction speed were investigated. SEM was used to observe the changes of the morphology of anhydrite powders before and after surface coating. The results show that the appropriate condition is: the concentration of Ca(OH)2 should be 2~3%, the temperature between 20~25°C is better, the revolution speed should be big enough and so on. In order to gain nanostructure surface, appropriate technological parameter should be chosen carefully. The SEM photographs show that Anhydrite powders had fine surface morphology after surface finish that the smooth cleavage planes were coated with nanometer particles and the sharp edge angles were blunt by the coating of CaCO3 nanometer particles.