The kinetics of endocrine disruptor 4-tert-butylphenol by chlorination in aqua was studied. The results showed that 4-TBP was rapidly oxidized by chlorine with different initial concentrations of HOCl and pH, and second-order reaction kinetics was observed between 4-TBP and chlorine. The apparent kinetic rate constants were influenced by pH values, and k(app) reached its highest and lowest level at pH 5 and 9 respectively. The kinetic rate constant of every elementary reaction was calculated. The rate constants for the acid-catalyzed reaction and the reaction between ClO- and 4-TBP were 4.99 x 10(6) L2 (mol min)(-1) and 1.96 x 10(4) L (mol min)(-1) respectively. The reaction between HOCl and 4-TBP or HOCl and 4-TBP- was very slow, and CIO- did not react with 4-TBP- . 4-TBP was influenced by chlorine disinfection during water treatment. The corresponding half-life time was 12.1 min when chlorine concentration was 3 mg/L.