The wave absorption performance of a new type of steel floating breakwater with truss (FBT), which is composed of a box-type pontoon and truss structures, has been investigated experimentally. The truss structures are attached to the front and the rear of the pontoon, and exaggerate wave energy dissipation due to wave breaking. Flow visualization has revealed that the front truss breaks the incident waves and effectively converts wave energy to turbulent energy. Image analysis of the motions of the FBT and determination of the transmission coefficient K_t showed efficient dissipation of wave energy resulting from the truss structure. K_t is also discussed and quantified with the aid of dimensional analysis. Values of K_t are plotted against the ratio of the water depth h to the wavelength of incident waves L, and the profiles obtained are normalized by introducing values of h/L at which K_t equals 0.5, i.e., (h/L)_0.5. Normalization gives a universal empirical expression for K_t, and empirical expressions of (h/L)_0.5 are also obtained by independently changing the shape parameters and the wave steepness. A graphic chart of (h/L)_0.5 is provided so K_t of the FBT can be evaluated easily. This data-reduction method developed for the quantification of K_t may be applicable for other floating breakwaters as well as for this new type.