Abstract: The by-product manganese sulfate in the production of hydroquinone in a chemical plant was studied with recrystallization，precipitation and direct heating in laboratory，and the content of bivalent manganese content was used for evaluation of purification effect. The results showed that both precipitation and direct heating could achieve separation and purification，but recrystallization could not achieve its desired effect of separation. Comparing the two methods，direct heating can achieve separation and can make full use of raw materials. Furthermore，after separation manganese sulfate and ammonium sulfate could be obtained，and direct heating is a simple method of separation.