Cefotaxime sodium is the third generation cephalosporins semisynthetic broad-spectrum antibiotics, in the reaction of cefotaxime sodium produced by cefotaxime acid, the valuable by- product acetic acid contained in the reaction liquid, ethyl acetate mother liquor. In the distillation of ethyl acetate liquor, the acidity of ethyl acetate was increased. By detecting the content of ethyl acetate, it is confirmed that the material of making the acidity ethyl acetate increased is acetic acid; through second distillation purification of ethyl acetate liquor, and using PROII software for distillation simulation, it is found that by distillation and PROII software simulation, ethyl acetate and acetic acid can be completely separated, the recycling can meet the certain quality indices of acetic acid (the content is more than 99% ), the yield is up to above 60%.