NOVELTY - A raw material is recovered in preparation of 7-phenylacetamido-3-(chloromethyl) cephalosporanic acid p-methoxybenzyl ester, by taking nitrogen doped ketone sulfinate, dioxane and toluene; adding chloropropane and slowly ventilating chlorine; distilling to remove dioxane and toluene; dissolving using dimethylformamide, cooling, adding liquid amino, stirring and reacting, adding hydrochloric acid and toluene, stirring until the solution is clarified, washing with hot water, and standing to make it stratified.    USE - Method for recovering raw material in preparation process of 7-phenylacetamido-3-(chloromethyl) cephalosporanic acid p-methoxybenzyl ester (claimed).    ADVANTAGE - The method has simple operation, is suitable for large scale production, and reduces environmental pressure.    DETAILED DESCRIPTION - Recovering raw material in preparation of 7-phenylacetamido-3-(chloromethyl) cephalosporanic acid p-methoxybenzyl ester, comprises:    (A) taking 100-300 g of penicillin sulfoxide ester, adding each form of 800-1200 pts. vol. of dioxane and toluene, taking ethanol and/or isopropyl alcohol (80-120 vol.% as solvent), adding 2-mercapto benzothiazole (50-100 pts.wt.), reacting for 2-5 hours at 80-120 degrees C, vacuuming to 0.1 atm, removing dioxane and toluene, adding isopropyl alcohol (800-1200 pts.vol.) to dissolve, dripping ethanol or isopropyl alcohol which can firstly dissolve the benzene sulfinate at 35 degrees C, dripping for 2-3 hours, cooling to 0 degrees C, insulating for 1-3 hours, washing with isopropyl alcohol, drying, obtaining nitrogen doped butanone sulfinic acid intermediate, collecting isopropyl alcohol eluent, performing post-processing, obtaining alcohol solution, adding 40-60 vol.% of organic solvent (C) under stirring condition, cooling to 0-5 degrees C, precipitating white solid, filtering, distilling the solvent of the filtrate, adding organic solvent (D), obtaining pale yellow solid (50-70 wt.%), performing recrystallization using 150-250 pts. vol. of mixed solvent of organic solvents (D) and (C), drying, and recovering 2-mercapto benzothiazole; and    (B) taking nitrogen doped ketone sulfinate (200-300 pts.wt.), dioxane (1000-1500 pts.vol.) and toluene (300-800 pts.vol.) as solvent, adding chloropropane (150-200 pts.vol.), stirring at 0-2 degrees C, slowly ventilating chlorine for 5-7 hours, vacuuming to 0.1 atm, distilling to remove dioxane and toluene, dissolving using dimethylformamide (600-1000 pts.vol.), cooling to - 45 to - 40 degrees C, adding liquid amino (30-80 pts.vol.), stirring and reacting for 0.5-1.5 hours, adding hydrochloric acid (150-200 pts.vol.) and toluene (1800-2000 pts.vol.), stirring until the solution is clarified, washing with 40-60 degrees C of hot water for 3-5 times, standing to make it stratified, obtaining organic layer and aqueous phase, conventionally treating the organic layer, obtaining 7-phenylacetamido-3-(chloromethyl) cephalosporanic acid p-methoxybenzyl ester, back extracting in the stratified aqueous phase using 1/3 of organic solvent (D), removing organic phase, cooling aqueous layer to 0-5 degrees C, freezing for 8-12 hours, and precipitating out the sheet crystal, which is the benzene sulfinate.