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With the rapid development of modern quantum mechanic theory and computer technology,quantum chemical calculation has been widely used in the investigation of the relationship for molecular structure and property,microcosmic reaction mechanism,and etc.From the point of theory view,all the characteristics of molecular and system could be implemented by computational chemistry and molecular simulation.In this work,we applied the Density Functional Theory(DFT) to study hydrolysis mechanism in alkaline solution,calculate reaction activation free energy barrier in rate-determining step,and establish rate constant equation for some organophosphate pesticides(methamidophos,paraoxon,parthion,and triazophos) and chemical warfare agents(sarin and tabun) with B3LYP/6-31+G(d,p) basis level and CPCM solvation model.The geometries of the reactants,transition states and products and reaction path were confirmed by vibration analysis and intrinsic reaction coordinate(IRC) method and the free energy surfaces,and their variation for rate-determining steps were established.Rate constant equations for all five compounds are calculated from 100K to 800K by applying of the Eyring transition state theory (TST) with Wigner correction at 1.0 Atm(101.325kPa),according to the following expressions 1 and 2.