Abstract: In order to overcome the traditional power MOSFET contradiction between on-state resistance and breakdown voltage, the super junction (SJ) device is introduced, so that it improves the breakdown voltage through the transverse electric field. In asymmetric pillar design requirements, establishing the asymmetry analysis model, introducing asymmetric factor k, analyzing the physical meaning of k and modifying the k value for pillar in different proportions, analytical expression of super junction is derived. In order to verify the accuracy of the design, basing on trench gate SJ-MOS device, simulation verification and comparison are carried out., theoretical and simulation results are in good agreement, the theory can be used as a guide for the design of super junction MOSFET.