The photo-induced reduction rate of m-nitroacetophenone (NAP) in the presence of TiO2 powder (anatase and rutile forms) is obtained by measuring the time-courses of the concentration of a product, m-aminoacetophenone (AAP). This photo-induced overall reaction in the ethanol is expressed as NO2C6H4COCH3 + 3C(2)H(5)OH --> NU2C6H4COCH3 + 3CH(3)CHO + 2H(2)O The photo-induced reduction rate of NAP is dependent on the TiO2 and initial NAP concentrations. The time courses of the AAP concentration normalized by the initial NAP concentration decrease with increasing initial NAP concentration. These characteristics can be interpreted by the non-linear differential equation as follows, d[AAP]/dt = k([NAP](0)-[AAP])(2k(0)t-6[AAP]) where [NAP](0), is the initial NAP concentration. The rate constants, k(0) and k, express the oxidation rate of ethanol and the reduction rate of NAP, respectively. The value of k(0) is dependent on the initial NAP and TiO2 concentrations. It takes a maximum value of 4.0 g/dm(3) for anatase and 1.0 g/dm(3) For rutile when the initial NAP concentration is about 1.0 mmol/dm. Then, the maximum value for anatase is 11.1 times that of rutile. The value of k(0) decreases with increasing initial NAP concentration. The k value is independent of the TiO2 and initial NAP concentrations, and the same value for both anatase and rutile forms is obtained.