<p>The wave attenuation capability of a porous floating breakwater for incident waves with different wave heights and frequencies is examined experimentally. In the experimental tests, the breakwater model is installed in a wave flume, and wave probes are arranged in front of and behind the breakwater to monitor the wave elevation time history which is used to validate the numerical model. Moreover, the PIV tests are also carried out in this experiment to monitor the velocity field behind the breakwater model to further verify the accuracy of the numerical calculation. Numerical simulation of the transmission coefficient as well as the velocity field behind the breakwater model under some cases tested in the experiment is performed. By comparing the numerical and experimental results, the accuracy of numerical simulation of the wave attenuation capability of the breakwater is validated. On this basis, the influence of the moment of inertia and size of the floating breakwater on its wave attenuation capability is analyzed numerically by performing a series of numerical tests. The results show that both size and moment of inertia of the breakwater will influence its wave attenuation performance. When the moment of inertia of the breakwater is adjusted (from <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(I^{\prime }=0.491\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>I</mi> <mo>′</mo> </msup> <mo>=</mo> <mn>0.491</mn> </mrow> </math></EquationSource> </InlineEquation> to <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(I^{\prime }=3.932\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>I</mi> <mo>′</mo> </msup> <mo>=</mo> <mn>3.932</mn> </mrow> </math></EquationSource> </InlineEquation>), the transmission coefficient of the breakwater will be reduced by 2.65–4.40%. When the size of the breakwater is changed (from <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(H/B=0.127\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>H</mi> <mo stretchy="false">/</mo> <mi>B</mi> <mo>=</mo> <mn>0.127</mn> </mrow> </math></EquationSource> </InlineEquation> to <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(H/B=0.155\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>H</mi> <mo stretchy="false">/</mo> <mi>B</mi> <mo>=</mo> <mn>0.155</mn> </mrow> </math></EquationSource> </InlineEquation>), its transmission coefficient will also change by 3.81% to 10.44%</p>