Real ocean waves are multi-directional irregular waves,and cylinder array with two tandem rows of four cylinders is one of the common structures in marine engineering.By numerical calculation,the variation of wave run-up,wave force and group coefficient are studied for eight large-scale cylinders (the ratio of the cylinder diameter D and the wave length λ,D/λ≥0.15) arranged in two tandem rows of four cylinders under the action of multi-directional irregular wave.The results indicate that the wave directionality has significant effects on the wave run-up and wave forces.Compared with the results of single tandem array of four cylinders at the same wave conditions,the normal wave force on cylinders in two tandem rows of four cylinders decreases,and the transverse force increases.Moreover,the cylinder spacing has a complex effect on the wave action on the cylinder array.The group effects will be small and can be ignored when the distance between two cylindrical centers is ten times the cylinder diameter.