A new type of floating breakwater (FB) is proposed in this paper. Its hydrodynamic performance has been tested. The structure of the newbreakwater named perforated semi-circular floating breakwater (SCFB) consists of two parts: a main body of a box-shaped base block and a semi-circular upper structure is perforated for the purpose of absorbing breaking and overtopping wave energy. A series of experiments were carried out on the new floating breakwater and traditional box floating breakwater to compare their performances. A two-dimensional wave flume was used in the experiment; the incident, transmitted, and reflected waves from the floating breakwaters were measured. Results showed that the new floating breakwater had a better performance than the traditional box floating breakwater: wave transmission was significantly reduced by the semi-circula upper part, especially for high waves.