The effects of barrier layer thickness, gate width length ratio and doping concentration on the transfer characteristics and transconductance curve of AlGaN/GaN HEMTs devices were studied by using Silvaco TCAD device simulation software. The results show that the change of barrier layer thickness can adjust the current switching ratio and threshold voltage of the device, and realize the transformation from depletion device to enhancement device. The ability of the gate voltage to control the two-dimensional electron gas in the quantum well increases with the increase of the gate width length ratio. The doping of barrier layer increases the output current and the peak value of transconductance, but the doping of too high concentration makes it difficult to turn off the device. This is of practical guiding significance for the practical preparation of GaN based HEMTs devices.