Starch acetate is a new starch based polymer for its application agent for controlling release cefotaxime sodium. Controlled release for oral cefotaxime are needed to stabilize cefotaxime sodium at pH of gastric, and to avoid irritating gastric with a degree of substitution of 2,75 could be synthesized by acetylation of cassava starch with acetic anhydride and acetic glacial using sodium hydroxide as catalyst. Starch acetate microcapsules of sodium cefotaxime were prepared by an emulsification-solvent evaporation method and the microcapsules were being studied evaluation of starch acetate as microencapsulating agent. The starch acetate microcapsules prepared are spherical shape. Microencapsulation efficiency depends on Degree substitution in 80,85 %.