This paper presents an approach to studing the economic dispatch of real power with N-1 security with the network flow programming (NFP), the N-1 line - security constraints are first introduced into the network f olw model and the problem of N-1 security economic dispatch becomes an incremental metwork flow model. Therefore, the shortage of NFP is mitigated to some extent, The solution adopted is the "out-of-kilter"algorithm(OKA), which is characterized by fast calculation and reliable convergency. The model and solution are tested on IEEE 30-bus system, and the results show that the proposed approach is feasible.