Characteristics of the natural wave cannot be successfully described by only using wave frequency spectra. In laboratory, natural wave conditions cannot be simulated exactly by harbour sheltering experiment with irregular long-crested waves, especially the results of diffraction tests with reflection source are often far away from the reality. So directional wave spectrum must be introduced to experiment on wave diffraction, except for one directional swell.At present, only a small number of laboratories in the world have possessed directional spectrum wave producer because of its complication and expension. This paper describes the experiment for multi-directional wave superposition of wave diffraction, with the conventional regular wave producer and one-direction irregular wave producer. The test results are of equal value with that from directional spectra wave. This method is suitable for rational design of harbour engineering projects and can be adopted in future practice. Characteristics of the natural wave can not be successfully described by only using wave frequency spectra. In laboratory, natural wave conditions can not be simulating by harbor long wave, especially the results of diffraction tests with reflection source are often far away from the reality. So directional wave spectrum must be introduced to experiment on wave diffraction, except for one directional swell. At present, only a small number of laboratories in the world have possessed directional spectrum wave producer because of its complication and expension. This paper describes the experiment for multi-directional wave superposition of wave diffraction, with the conventional regular wave producer and one-direction irregular wave producer. The test results are of equal value with that from directional spectra wave. This method is suitable for rational design of harbor engineering projects and can be adopted in future practice.