The influence of gate-head and gate-source-spacing on the performance of AlGaN/GaN HEMTs was studied. Suggestions are then made to improve the performance of high frequency power AlGaN/GaN HEMTs by optimizing the gate-structure.Reducing the field-plate length can effectively enhance gain,current gain cutoff frequency and maximum frequency of oscillation.By reducing the field-plate length,devices with 0.35μm gate length have exhibited a current gain cutoff frequency of 30 GHz and a maximum frequency of oscillation of 80 GHz.The maximum frequency of oscillation can be further optimized either by increasing the gate-metal thickness,or by using aτ-shape gate (the gate where the gate-head tends to the source side).Reducing the gate-source spacing can enhance the maximum drain-current and breakdown voltage,which is beneficial in enhancing the maximum output power of AlGaN/GaN HEMTs. The influence of gate-head and gate-source-spacing on the performance of AlGaN / GaN HEMTs was studied. Suggestions are then made to improve the performance of high frequency power AlGaN / GaN HEMTs by optimizing the gate-structure. Reducing the field- plate length can effectively enhance gain, current gain cutoff frequency and maximum frequency of oscillation. By reducing the field-plate length, devices with 0.35 μm gate length have been loaded a current gain cutoff frequency of 30 GHz and a maximum frequency of oscillation of 80 GHz . The maximum frequency of oscillation can be further optimized either by increasing the gate-metal thickness, or by using aτ-shape gate (the gate where the gate-head tends to the source side). Reducing the gate-source spacing can enhance the maximum drain-current and breakdown voltage, which is beneficial in enhancing the maximum output power of AlGaN / GaN HEMTs.