In　this　paper,　we　use　Silvaco-ATLAS　two-dimensional　numerical　simulation　to　calculate　the　performance　of　two　different　circular-gate　AlGaN/GaN　HEMT　device　models.　The　influence　of　the　special　circular-gate　structure　on　the　DC　characteristics　of　the　AlGaN/GaN　HEMT　device　is　studied　and　compared　with　that　of　conventional　devices.　Compared　with　conventional,　the　threshold　voltage　of　the　drain-center　and　source-center　circular-gate　devices　increased　from　1.1　V　to　1.5　V,　while　the　transconductance　improved　from　245　mS　mm-1　to　328　mS　mm-1　and　285　mS　mm-1　respectively.　In　the　on-state　of　devices,　the　maximum　saturation　output　current　increased　from　536　mA　mm-1　to　620　mA　mm-1　and　650　mA　mm-1　.　Furthermore,　the　breakdown　voltage　of　the　source-center　circular-gate　device　rose　from　765　V　to　870　V　compared　to　conventional　devices;　however,　for　the　drain-center　circular-gate　device　it　was　only　at　685　V　due　to　concentrated　electric　fields　outside　the　drain　region-this　limitation　can　be　effectively　addressed　by　increasing　the　drain　area.　Simulation　results　demonstrate　that　circular-gate　AlGaN/GaN　HEMT　devices　can　avoid　edge　effects,　improve　electric　field　distribution,　and　alleviate　self-heating　effects.