In the coherent beam combination of lasers array,the duty ratio has influence on efficiency of coherent beam combination,which is researched with mathematic analysis. Coherent beam combination experiment with 1×2 laser arrays is carried out in self-Fourier cavity. The result of mathematic analysis shows that through increasing the duty ratio,the energy duty of the central spot increases,and the number of secondary spot decreases.It is proved by the results of experiment that the energy duty of the central spot decreases from 42% to 11.13%,when the distance of two adjacent beam increases from 2.06 mm to 6.02 mm.