Aimed at the problems that discharge mechanisms are complex and discharge characteristics of helicon wave plasma sources are unclear, this paper systematically investigates the discharge characteristics of working gases such as argon,helium,and nitrogen,as well as the effects of magnetic field strength,RF power,and gas pressure on argon discharge properties by the RF-compensated Langmuir probe diagnostic method. The experimental results indicate that argon exhibits optimal performance in terms of discharge intensity and ion density,making it more suitable for electric propulsion systems.A magnetic field is necessary for the transition from inductive discharge to wave-coupled mode.Under condition of specific parameters (0.40 Pa,200 G),there undergoes a H-W mode transition 600 W around in the process of argon discharge, with ion density reaching the order of 1018 m-3 in the wave mode. Although appropriately increasing the discharge gas pressure can enhance power coupling efficiency and discharge intensity,yet when thepressure exceeds a certain level,the increase in ion density slows down or even saturates. The conclusions demonstrate that the mode transition in helicon discharge is closely related to external parameters,and this study provides experimental evidence for elucidating its physical mechanisms and propulsion applications.