This paper reports on application of network flow programming to the real power economic redispatch with security constraints. For the contingency state which violates the line security constraints , the re-dispatching is performed by eliminating the curtailment of real loads. The network flow model is incremental, and is solved by OKA. Therefore, it is very simple, fast and accurate. The model and its solution algorithm are tested on JEEE 30 bus system and the encouraging results are obtained.