Nowadays humankind is seeking relative peace in seashores. Breakwaters are mainly considered as one of the most important structures which provide a safe area at the beaches. Although, a variety of fixed breakwaters were used in the former days, the economical, pragmatic and environmental limitations of these breakwaters lead to utilize of floating breakwaters as an alternative option in the last three decades. The main aim of this study encompasses the effect of different parameters such as wave height, wave period and water depth, accompanied by the geometrical parameters such as the width of the structure, water draught and the section shape of floating breakwater on the behavior and efficiency of floating breakwaters. Open source software called OPEN FOAM is used to study the flow pattern in the vicinity of floating breakwater by a numerical method. In this study the numerical modelling is conducted in two-dimensional (2D) form on fixed floating breakwaters in the wave flume subjected to regular wave in deep water. The results indicated that increase in wave height, width of structure and water draught lead to an increase in floating breakwaters performance. An increase in wave period causes a high wave passing and subsequently a decrease in fixed rectangular breakwater's performance. Also, as the water depth increases, the height of passing wave will be decreased. In order to make a comparison of the transmission coefficients between rectangular and trapezoidal fixed floating breakwaters, we can conclude that the trapezoidal breakwater performed better than the rectangular one, and also the wave height will be increased due to increase in the side inclination of breakwaters structure. Keywords : wave, floating breakwater, wave passing coefficient, numerical simulation, OPEN FOAM.