This paper presents the results of comparison of impact pressures on open-plied structures induced by regular waves and irregular waves in a laboratory channel. Regular waves with wave heights ranging from 0.1～0.2 m and periods ranging from 1.0～2.0 s are tested. The target spectrum for the irregular wave is JONSWAP spectrum. Irregular waves with significant wave heights in the range of 0.10～0.25 m and peak periods in the range of 1.0～2.0 s are tested. The relative clearance s/H 1/3(H) is between -0.1 and 0.4, s being the subface level of structure model above the still water level. Time series of impact pressure are analyzed to indicate whether the property of impact pressures induced by the regular wave significantly deviates from that by the irregular wave. The distribution of the impact pressure along the underside of the structure is compared for different types of incident waves. The effects of wave parameters, structure dimension and structure clearance on the impact pressure are also discussed. This paper presents the results of comparison of impact pressures on open-plied structures induced by regular waves and irregular waves in a laboratory channel. Regular waves with wave heights ranging from 0.1 ~ 0.2 m and periods ranging from 1.0 ~ 2.0 s are tested. The target spectrum for the irregular wave is JONSWAP spectrum. Irregular waves with significant wave heights in the range of 0.10 ~ 0.25 m and peak periods in the range of 1.0 ~ 2.0 s are tested. The relative clearance s / H 1/3 (H) is between -0.1 and 0.4, s being the subface level of structure model above the still water level. time series of impact pressure are analyzed to indicate whether the property of impact pressures induced by the regular wave significantly deviates from that by the irregular wave. The distribution of the impact pressure along the underside of the structure is compared for different types of incident waves. The effects of wave parameters, structure dimension and structure clearance on the impact p ressure are also discussed.