Hydrolysis of tri-p-methoxyphenyl phosphate ester (tri-p-MPPE) was studied in micelle medium of cetyl tri methyl ammonium bromide n-C16H33N+ (CH3)3Br (CTABr) at pH-9.0. The hydrolysis followed first order kinetics with respect to tri-p-MPPE concentration. At the critical micelle concentration (CMC) the rate of hydrolysis increased with increasing with increasing CTABr concentration. Micelle with cationic or polar head group form micelle in water with hydrocarbon like interior or polar groups at the surface and bind cationic solute. The binding constant of micelle for tri-p-MPPE and the rate constant in micelle pseudo phase were determined from kinetics data using the pseudo phase model.