Network DEA models have been widely used in dealing with performance measurement of complex organizations and systems with multiple processes and multiple sub-systems． In real situations where intermedi-ate products produced by first stage can not be consumed completely by second stage，traditional DEA models overvalues system efficiency while current network DEA models underestimate system efficiency． This paper put forwords two-stage efficiency models，where part of the intermediate products are viewed as final products and entered into distribution channels，and depicts real performance of two-stage production process． This pa-per provides product forms to characterize cooperation of the two stages and discusses both upper and lower ef-ficiency bounds of various stages． A linear programming model is converted from non-linear efficiency model by considering one of the efficiencies of the stages as a parameter． The model is illustrated by a numerical evaluation of the bank’s performance．