Abstract: A novel technique of optimal design of a chemical reactor was deve-loped based on modern control theory and optimal Hamiltonian function By examining the controllability of a given reaction system,it is po-ssible to predict whether or not the design requirements can be simultan-eously satisfied without knowing the temperature and concentration profiles inside the reactor.If control vector can be explicitly solved by optimal Hamiltonian function,the design algorithm Willl be converted to BVP.The only policy which optimizes the Hamiltonian function is that the control vector reaches its upper and/or lower bounds if Hamiltonian function is linear in control variables.