Abstract: Energy loss inevitably occurs in the process of conversion and application of electric energy, and the core part of power control and power conversion process is power electronic devices. GaN quasi-vertical MOSFETs have the advantages of high input impedance, fast switching rate and less sensitivity to surface state traps, thus becoming the focus of current research. However, due to the low mobility of channel carriers, the on-resistance and loss are large. In this paper, the simulation of the re-grown channel GaN quasi-vertical MOSFETs proves that the structure can effectively solve the problem of low channel carrier mobility. Then, the structure of the re-grown channel GaN quasi-vertical MOSFETs is improved to optimize the carrier distribution in the source region and drift region. In the source region, the current conduction path of source region is effectively shortened by etching the Al2O3 below the metal cap of the source electrode; in the drift region, a layer of carrier distribution layer is inserted below the gate electrode to make the carrier distribution in the drift region more uniform. A new re-grown channel GaN quasi-vertical MOSFET with a threshold voltage of 2.3V was designed, with specifications of on-resistance as low as 1.8mΩ·cm2 and breakdown voltage as high as 1053V.