The mechanism of optical isomerization of valine molecules with dual-hydrogen bonds between amino and carboxyl groups and the damage induced by hydroxyl radicals in water environment were studied by using MP2/6-311++G(2df

pd)// B3LYP/6-31+G(d

p) dual-theory and SMD model method for self consistent reaction field (SCRF) theory. The study of reaction channels showed that there were three channels a

b and c in the optical isomer reaction of valine in water environment. Using water cluster as medium

the protons transfered from one side of the α-carbon to the other side with N atom of amino group

O atom of carbonyl group and carboxyl group as bridges. The hydrogen abstraction reaction which damaged the valine molecules happened in channel a

and the water molecules were assistants. The potential energy surface calculation showed that when two or three water clusters were used as hydrogen transport medium

they acted a good catalytic action on the process of hydrogen-transfer of Optical Isomerization

and reduced the barrier of reaction vs naked reaction. Water solution effect had good catalytic activity in channel a

but catalytic activities were not obvious in channel b and c. The reaction barrier of hydrogen abstraction reaction which damaged the valine molecules with water molecules as assistants was low. The water solution effect has a big impediment effect on this reaction.