This paper presents a physical experiment study on caisson breakwater with contracted channel and OWC (Oscillating Water Column) modeling. The form of channel structure, factors of incident wave and shape parameters of OWC air chamber have a great influence on the work efficiency of this composite structure, how they affect the composite structure is observed in the experiment by changing them and analyzed the test date. The work efficiency of the structure is expressed by wave amplitude amplification factor, point-pressure on the top of OWC chamber and wave reflectivity before the breakwater.