The main goal of the structural optimization is to minimize the weight of structures while satisfying all design requirements imposed by design codes. This paper implements the recently developed meta-heuristic algorithm Water Wave Optimization (WWO) for the size optimization of truss structures with discrete variables. The WWO algorithm is inspired by the theory of water waves and uses a series of processes such as propagation, refraction and breaking for searching in a highly-dimensional solution space. The performance of the WWO is demonstrated through five classic optimization problems of truss structures with discrete variables. Optimization results demonstrate the excellent performance of the WWO algorithm in terms of both optimum solution and the convergence in comparison with other optimization methods documented in literature.