In order to improve the security of scheduling decision and enhance its ability to deal with occasional line contingencies, a two-stage robust unit commitment model considering N-k network security constraints is proposed . Firstly, two kinds of N-k uncertainty sets used in the current research are introduced, and the characteristics of the set are described. Secondly, based on the two kinds of N-k uncertainty sets, a general form of two-stage robust unit commitment model is constructed. The formulation is divided into two stages, where the first stage is the unit commitment decision before the line contingency, and the second stage is the economic dispatching decision as the worst case of line contingencies are observed. The first and second stage problems are reformulated into a master problem and sub-problem, respectively, So that the column-and-constraint generation (C& CG) algorithm can be used to solve the proposed two-stage unit commitment model in an iterative manner. By using linearization techniques and duality theory, both the master problem and the sub-problem can be converted into mixed integer linear programming (MILP). Finally, the validity of the proposed model was verified by the calculation and analysis of the IEEE 14 bus and IEEE 118 bus systems.