A suspension bridge is the most suitable type for a long-span bridge. Increased kinematic displacements are the major disadvantage of suspension bridges. This problem can be solved by application of prestressed cable truss. Dynamic approach is one of regulated bridge design parts. Simplified determination method of natural-vibration frequencies of prestressed suspension structure and its experimental validation is presented in this paper. Natural-vibration frequencies and mode shapes of the model depending on the prestressing level were determined. It was experimentally proved, that mode shape with one half-wave does not appear for the model. The difference between results, which were calculated by the developed simplified determination method of natural-vibration frequencies of prestressed suspension structure and experimentally achieved by the model testing, does not exceed 20%. Therefore the method is applicable for preliminary dynamic analyses of structures.