A method was established for preparing calcium sulfate dehydrate whiskers under normal pressure and low tem-perature conditions（T<90 ℃） using the intermediate by-product CaCl₂ from the leachate of phosphate ore by hydrochloric acid as raw material.The effects of different crystal shape control agents on the morphology and aspect ratio of the calcium sulfate whiskers were investigated and the samples prepared were characterized by FESEM and XRD.DTAB was selected as the more suitable crystal form control agent.The conditions of DTAB dosage,reaction temperature and concentration of Ca²⁺etc. were optimized.The optimum process conditions were determined as follows:DTAB dosage was 3%,reaction temperature was 90 ℃,the concentration of Ca²⁺ was 0.1 mol/L,reaction time was 25 min,and the amount-of-substance ratio of calcium to sulfur 1:1.1.Under the conditions,the L/D ratio of as-prepared calcium sulfate whiskers achieved 130.The obviously enhanced intensity of the（020） and（040） crystal planes in X-ray diffraction patterns of the whiskers sample showed preferential gro-wth along the normal direction of the（040） crystal plane.The action mechanism of the crystal shape controlling agent was preliminarily discussed based on the spiral growth theorem.