Abstract: To study the attenuation behavior of ozone in water, two methods were used to measure ozone concentration in water, indigo disulphonate spectrophotometry (IDS)and iodine titration method(ITM). The results of IDS were: when pH 2.0, the absorbency of black dropped by 3%, the absorbency of sample dropped by 40%; at pH 6.8, dropped by 1% and by 2%, respectively; at pH 11.9, dropped by 83% and by 52%, respectively; this implied that condition of this method used to measure the ozone concentration in water needed to be studied further. The results of ITM were: the trend of the ozone concentration in distilled water was declining, and its speed before and after 15～42 min after ozonation was different; the trend of the ozone concentration in tap water and nutrition solution was steady, which was different with distilled water; The ozone concentration was: about 3 mg/L(in nutrition solution)