Abstract: Objective:To determine the preparation technology of mutant K253Q arylsulfatase(from Pseudoalteromonas carrageenovora)modified agar and to characterize its properties. Methods:Taking the sulfate removal rate as the evaluation index,the effects of reaction time,enzyme dosage,temperature and pH on the treatment of agar by mutant arylsulfatase K253Q were investigated,and the physical and chemical properties and structure were characterized. Results:4 g agar was used as raw material. The optimum conditions were as follows:reaction time 6 h,enzyme amount 80 U reaction temperature 50 ℃,initial pH7.0. In addition,100 g agar was used as the raw material for the scale-up experiment. Under the optimum conditions,the sulfate removal rate was up to 50.1%. Under these conditions,the gel strength,3,6 anhydrogalactose,whiteness and transparency of agar increased significantly after K253Q treatment,while ash and viscosity decreased significantly(P<0.05). SEM analysis showed that the surface of K253Q treated agar was more connected and the surface was smoother. Conclusion:Agar treatment with K253Q enhanced the quality of agar,decreased the content of agar sulfate,increased gel strength,3,6 anhydrogalactose,whiteness and transparency,and reduced ash content.