The present study theoretically as well as experimentally investigates the interaction between waves and an array of porous circular cylinders with or without an inner porous plate based on the linear wave theory.To design more effective floating breakwaters,the transmission rate of waves propagating through the array is evaluated.Each cylinder in the array is partly made of porous materials.Specifically,it possesses a porous sidewall and an impermeable bottom.In addition,an inner porous plate is horizontally fixed inside the cylinders.It dissipates the wave more effectively and eliminates the sloshing phenomenon.The approach suggested by Kagemoto and Yue(1986) is adopted to solve the multiple-scatter problem,while a hierarchical interaction theory is adopted to deal with hydrodynamic interactions among a great number of bodies,which efficiently saves computation time.Meanwhile,a series of model tests with an array of porous cylinders is performed in a wave basin to validate the theoretical work and the calculated results.The draft of the cylinders,the location of the inner porous plate,and the spacing between adjacent cylinders are also adjusted to investigate their effects on wave dissipation. The present study theoretically as well as experimentally investigates the interaction between waves and an array of porous circular cylinders with or without an inner porous plate based on the linear wave theory. To design more effective floating breakwaters, the transmission rate of waves propagating through the array is evaluated.Each cylinder in the array is partly made of porous materials.Specifically, it possesses a porous sidewall and an impermeable bottom. In addition, an inner porous plate is horizontally fixed inside the cylinders .It dissipates the wave more effectively and eliminates the sloshing phenomenon. The solution suggested by Kagemoto and Yue (1986) is adopted to solve the multiple-scatter problem, while a hierarchical interaction theory is adopted to deal with hydrodynamic interactions among a great number of bodies, which efficiently saves the computation time. a series of model tests with an array of porous cylinders is performed in a wave basin to validate the theore tical work and the calculated results. the draft of the cylinders, the location of the inner porous plate, and the spacing between adjacent cylinders are also adjusted to investigate their effects on wave dissipation.