The invention relates to the technical field of semiconductor device manufacturing, and discloses a low-damage GaN/AlGaN HEMT gate groove etching method. The low-damage GaN/AlGaN HEMT gate groove etching method includes the steps: forming an etching barrier layer on a GaN/AlGaN HEMT epitaxial structure; performing imaging on the etching barrier layer, and exposing the preset surface of the GaN/AlGaN HEMT epitaxial structure of the gate part; and putting the exposed preset surface of the GaN/AlGaN HEMT epitaxial structure of the gate part in an etcher immersed in the etching gas of HBr and He,and applying bias voltage to etch the preset surface of the GaN/AlGaN HEMT epitaxial structure of the gate part to the specified depth to form a gate groove structure, thus reducing the influence of etching particles on the gate groove of GaN/AlGaN HEMT, reducing the etching damage of the gate groove and improving the electric property and the yield rate of devices.