Abstract: The ability to generate hydroxyl radicals of the different electrolyzed water and the sodium hypochlorite solution in the process of storage was investigated.The results showed that the changes of p H did not affect the ability of electrolyzed water to generate hydroxyl radicals when the available chlorine concentration was 17 mg / L.When the available chlorine concentration was 60 mg / L,the ability to generate hydroxyl radicals increased with the p H increasing,the hydroxyl radicals in slightly acidic electrolyzed water did not change significantly within 0~24h,the concentration of hydroxyl radicals reached the maximum when the storage time of 5h both at 17℃ and 4℃.At the different p H and the available chlorine concentration,and the capacity of electrolyzed water to produce hydroxyl radicals was stronger than that of sodium hypochlorite solution.