Breakwaters are an important structure of port and coastal engineering. Compared to traditional rubble mound breakwaters or caisson breakwaters, floating breakwaters can adapt to situations with deeper water, soft foundations, large tidal ranges, and the needs of water exchanges. Floating breakwaters have broad application prospects in port and coastal engineering, offshore engineering, aquaculture, and many other fields. This paper starts with the structure of a traditional single pontoon floating breakwater anchored by chains. By 2D physical model experiments conducted in a wave flume, the wave-damping performance of structures of single pontoon, free twin pontoons, rigidly connected twin pontoons, and twin pontoons combined with plates was compared and analyzed with the test results of wave transmission coefficients. The research results indicate that, the wave transmission coefficients of the rigidly connected twin pontoons are less than those of the single pontoon and free twin pontoons, and the floating breakwater structure combining twin pontoons with vertical plates can further enhance the wave-damping performance.