Acetone solvate of dimethoxydocetaxel or 4-acetoxy-2α-benzoyloxy-5β,20-epoxy-1-hydroxyl-7β,10β-dimethoxy-9-oxotax-11-en-13α-yl(2R,3S)-3-tert-butoxylcarbonylamino-2-hydroxyl-3-phenylproionate and its preparation by crystallization from an aqueous/acetone solution.本發明係關於二甲氧基克癌易或4-乙醯氧基-2α-苯甲醯氧基-5β,20-環氧基-1-羥基-7β,10β-二甲氧基-9-酮基紫杉-11-烯-13α-基(2R,3S)-3-第三丁氧羰基胺基-2-羥基-3-苯基丙酸酯之丙酮溶劑合物及其由水性/丙酮溶液結晶之製法。