In this paper, a spontaneous self-organized pattern in atmospheric pressure barrier discharge driven by pulse-modulated radio frequency (rf) power is reported with the help of a self-consistent 2-D fluid model. Under the action of pulse-modulated rf voltage with proper duty cycle, the filaments come into being, and at last four stable discharge channels are observed. The formation of self-organized filaments can be sequentially divided into three stages: preionization stage, discharge self-adjusting stage, and pattern formation stage. In the preionization stage, it exhibits homogeneous characteristics; in the discharge self-adjusting stage, discharge instability is magnified, and four filaments turn up; in the pattern formation stage, discharge channels are fixed at the same locations permanently. In addition, we widen the electrode plate and find out that the number of the self-organized discharge channels increases, while the adjacent channel distance is almost a constant as the width of the plane increases.