With economies of scale as the objectives and constraints, the optimal allocation of enterprises' asset structure was discussed. The main contributions of this paper are as follows: (1) Economic efficiency of scale from 2007 to 2011 in various sub-industries of manufacturing was obtained. (2) After empirical analysis and comparative study of the relationship between economic efficiency of scale and asset structure, we arrived at optimization direction of the enterprises which are at economies scale and diseconomies scale.