The purpose of this research to present for the first time a practical plan to cost optimize the composite metal floor deck, so that the designer, by having the dimensions of the main beam framing, will be able to come to the most design including: the section of composite steel beam, the beam span, the thickness of metal deck sheets and the thickness of the concrete slab. The main method of optimization by using metaheuristic algorithm is harmony search which its objective function is equal with these costs: steel beam, metal deck and concrete slab in one square meter of the floor. The standards of this design is according to SDI code and the Iranian National Building Code, Part 10: Design and Construction of steel buildings -allowable stress method. In this design all the metal beam profiles are the common and practical sections in building industry. Also the chosen metal deck, by the brand name Sundeck 75, is the most economical metal deck produced in the country Iran which is invented by the writer 1 and has been confirmed by Road, housing and Development Research center. In the end to ensure all the results of the harmony search optimization, several questions has been optimized, so the comparison of its results with the harmony algorithm results indicates that the high convergence in this algorithm.