Preparation method of metiram

The invention discloses a preparation method of metiram, which comprises the following steps: adding an aqueous solution of dithane into a four-mouth bottle, heating to 20-35 DEG C, and dropwise adding hydrochloric acid to adjust the pH value for later use; adding a zinc sulfate aqueous solution into the reaction container, heating to 30-45 DEG C, dropwise adding the pH-adjusted ambam aqueous solution, and preserving heat for 0.5-1 hour after dropwise adding is finished; and dropwise adding a sodium hypochlorite aqueous solution into the system after heat preservation is finished, preserving heat for 0.5-1 hour after dropwise adding is finished, dropwise adding ammonia water into the system to adjust the pH value, then adding a stabilizer, preserving heat for 1-2 hours, and sequentially filtering, leaching, adding the stabilizer and drying to obtain the metiram active compound. Sodium hypochlorite is adopted as an oxidizing agent, and no inorganic acid needs to be added in the oxidation process; after the rea