Abstract: As a high-density low-temperature plasma, helicon plasma offers distinct advantages such as high electron density, no electrode erosion, high ionization efficiency, and strong controllability, showing promising prospects in electric propulsion, materials processing, nuclear fusion, and other fields. This paper systematically reviews several key fundamental issues in helicon plasma discharge physics over the past five years, with emphasis on the mode coupling mechanism between helicon and Trivelpiece–Gould waves, the density peak under low magnetic field (low-field peak) phenomenon, the formation and characteristics of double layers, discharge mode transitions and their hysteresis behavior, other extensive argon-related research, as well as the current status of application-oriented research of non-argon working gases. Future work needs to develop comprehensive numerical models and diagnostic techniques with high spatial and temporal resolution, and to expand systematic investigations under multiple working gases and magnetic field configurations, so as to promote the synergistic advancement of fundamental understanding and applied development.