Abstract Firstly,this paper deeply analyzed the chemical process in chlorine water system,aimed to clear the chlorine water was composed of a variety of molecules,ions and free radicals in the complex redox system; secondly,designed six experiments for scientific inquiry on chlorine bleaching effect under different conditions,and gave a reasonable explanation for the experimental results; finally,scientifically summed up the bleaching effect of chlorine water was a process of multiple components of synergy with many influence factors,but the "hero" was still hypochlorous acid,and gave corresponding scientific explanation.