The curved slit caisson breakwater is a kind of perforated-wall caisson with an arc-shaped slit wall, The caisson is very stable against storm waves and can dissipate large amount of wave energy. However, wave force acting on the arc-shaped slit wall outwards from inner side of the water chamber is impulsive.
　Curved double slit caisson is invented to improve the curved slit caisson breakwater and reduce the impulsive force. The curved double slit caisson has the second vertical slit wall with a rear wave chamber.
　It is expected that the curved slit caisson can reduce wave force more.
　A series of model experiment has been carried out to investigate the characteristics of the curved double slit caisson breakwater. Major conclusion of experiment are as follows:
1)The curved double slit caisson can dissipate wave energy more efficiently than the curved double slit caisson with same radius.
2)Wave ressure distributions are ptoposed.
3)The curved double slit caisson can reduce the impulsive pressure and also total weight of the curved double slit caisson breakwater required for stability.