The researches on multi-level programming models have gradually become one of the most promising research fields in operational research, and have been widely used in many fields. In this paper the theoretical background, basic definitions, and basic properties of multi-level programming models are introduced. Then, the basic principles, basic models, solution processes and characteristics of gravity search algorithm are introduced in detail. Taking a bi-level programming model as an example, the basic method of solving multi-level programming problem is proposed based on gravity search algorithm. In order to verify the validity and the feasibility of the proposed solving method, the multiple test functions, including continuous linear bi-level programming problem, integer linear bi-level programming problem and nonlinear bi-level programming problems, are used to investigate the performances of gravity search algorithm to solve multi-level programming models. The results show the high performances of the proposed method.