The Hydrolysis kinetics of Benzoyl Styrene Derivatives[I]${sim}$[IV] was investigated by ultraviolet spectrophotometery in 5% dioxane-$H_2O$ at $40^{circ}C$. The structure of these compounds were ascertained by means of ultraviolet, melting point, IR and NMR spectra. The rate equations which were applied over a wide pH range (pH $1.0{sim}13.0$) were obtained. The substituent effects on Benzoyl styrene derivatives[I]${sim}$[IV] were studied, and the hydrolysis were facilitated by electron attracting groups. On the basis of the rate equation and substitutent effect and final product, the plausible hydrolysis reaction mechanism was proposed: At pH 1.0${sim}$pH 9.0, not relevant to the hydrogenl ion concentration, neutral $H_2O$ molecule competitively attacked on the double bond. By contrary. Above pH 9.0, It was proportional to concentration of hydroxidel ion.