Helicon plasma sources have gradually been widely adopted in various research fields due to their high ionization efficiency and high density. Lacking in understanding of the mechanism for the high ionization efficiency and the power coupling mode of helicon discharge has been a great challenge for scholars to deal with in this field. To diagnose the discharge process and the characteristics is an important way to reveal its physical mechanism. Spectral diagnosis can avoid the interference of contact measurements on plasma and is free from plasma ablation. It responds quickly and is flexible to operate. In order to study the discharge characteristics of helicon plasma and the influence of gas pressure, researches on emission spectral diagnosis of argon discharge and numerical simulation of the Helic code for these experiments were conducted. The radial profiles of the line intensity were obtained by changing the focal length of the fiber optic probe to adjust the radial diagnostic position. Atomic emission lines of argon are mainly concentrated in the 740～920 nm region, which are generated by the transition of argon atoms between the 4p-4s energy levels and stronger than the relative intensity of ion lines. It can be found that at lower pressure ranges (0.2 Pa