Abstract: The exergetic analysis was carried out for reaction system of ethyl benzene dehydrogenation to styrene in an adiabatic reactor with an energy transfer-conversion model for complicated system. With an exergy flux chart of system instead of structure characteristics, analysis of system and mathematical computation could be simplified. Energy model was formulated for this system. The expression of mutual relationship between general exergy efficiency of system and exergy efficiency of energy unit was derived. The concept of enthalpy exergy at high temp. and enthalpy exergy at low temp. was discussed. The general exergetic efficiency of system, and exergy efficiency of each energy unit as well as contribution coefficient of exergy efficiency of energy unit were calculated. The main direction of energy saving could be Settled. The analysis results accorded with the data from factor practice.