Sodium oleate modified anhydrous calcium sulfate whiskers can not only enhance the hydrophobicity of anhydrite whiskers, but also introduce -C=C- groups on the surface of whiskers to increase its functionality. The influence of sodium oleate dosage, modification time and modification temperature on the modification effect was investigated by using the dispersion property of whisker in methyl methacrylate (MMA). The adsorption and modification mechanism of whiskers were explored by XRD, XPS and DRIFTS, the hydrophobicity of whiskers were determined by Washburn method. The results show that with the increase of sodium oleate dosage, the dispersion performance first becomes better and then becomes worse. When the mass ratio of sodium oleate to whisker is 1∶100, the settling height and settling velocity are greatly increased from 3.1 cm and 0.31 cm/min when the mass ratio of sodium oleate to whisker is 1∶200 to 10.6 cm and 1.06 cm/min, and the amount of sodium oleate when the dispersion performance starts to change suddenly increases with the temperature. DRIFTS show that oleate ions are mainly combined with calcium ions on the surface of the whiskers by physical adsorption and chemical adsorption, their characteristic absorption peaks are double peaks at 1 577 cm-1and 1 540 cm-1, and a single peak at 1 547 cm-1. The hydrophobicity of the modified whiskers is greatly increased compared with that before modification, and the contact angle with water increased from 0.04° before modification to 77.35° after modification.