Extending the work of reference 3, this paper also indicates a general algorithm to calculate the gradient of DEA efficiency for inefficient DMUs within the empirical production set, in which all inputs and outputs of the inefficient DMUs are simultaneously changed to make them efficient DMUs.

The equivalence between Russell input technical efficiency and DEA efficiency is proved in this paper.

The DEA efficiency, scale benefits, input redundancy and output lack are analyzed.

Through the DEA efficiency analysis and scale efficiency analysis, we measured the listed companies efficiency effectively.

New Model for Justifying DEA Efficiency of Decision-Making Units;

According to the analysis of DEA efficiency and scale benefits of each DMU, the situation of production of each year is evaluated, to further evaluate the management efficiency of Yangzhou Port.

Some qualities of the DMU which is a level DEA efficient have been presented as well.

For a non DEA efficient (C2R or C2GS2) Decision Making Unit (DMU), this paper gives a method, which is to increase its outputs by same suitable tiines with its unchanged inputs, and by which this DMU is rendered DEA efficient when original DEA efficient DMUs are DEA efficient yet.

This article indicates that the new method in references [1] and [2] can not completely discriminate the DEA efficiency and weak DEA efficiency of DMUs,furthermore,the optimal solution of DEA models used in the new method might not exist,which demonstrates the limitation of the application of the new method.

On the basis of the theory of partially ordered sets, some characteristic properties of weak DEA efficiency on four DEA models are given in this paper.