Remote plasma can effectively avoid the etching effect caused by electron-ion collision, improve the free radical reaction, and achieve a better modification effect. All of which have important applications in the field of membrane materials. In order to study the electron states and their variation laws in remote plasma, emission spectroscopy was used to diagnose the remote Ar plasma. Further, the effects of RF power, the pressure inside the reaction chamber, and distance from the discharge center on the emission spectral intensity, electron density, and electron temperature of the remote Ar plasma were also investigated. The results show that the characteristic peaks are more concentrated in the 690～890 nm region, which is dominated by ArⅠ atomic spectral lines, and that the variation pattern of the intensity of the spectral lines is the same as that of the electron density. The electron temperatures at different discharge parameters were calculated using the Boltzmann slope method and three selected ArⅠ spectral lines. The electron temperature changes with the change in the RF power, the pressure inside the reaction chamber, and the distance from the discharge center. When the RF power is increased from 30 to 150 W, the electronic temperature drops from 3 105.39 to 2 552.91 K. When the pressure rises from 15 to 25 Pa, the electron temperature drops from 3 066.53 to 2 593.32 K, then rises to 2 661.71 K when the pressure increases to 35 Pa. The electron temperature increases from 0 to 10 cm from the discharge center due to the increase in plasma potential, while after 10 cm, the electron temperature decreases and tends to 0 K at 80 cm from the discharge center. By analyzing the Stark spread of the Ar Ⅰ 696.894 spectral line, the electron density of the remote Ar plasma was calculated, and it was discovered that the electron density is up to 1016 cm-3 in order of magnitude. When the RF power was increased from 30 to 150 W, the electron density increased from 2.15×1016 to 2.88×1016 cm-3, from 2.36×1016 to 2.90×1016 cm-3 when the pressure was increased from 15 to 25 Pa, and decreased to 1.89×1016 cm-3 when the pressure was increased to 35 Pa. The electron density decreases rapidly as the axial distance increases, reaching 0 cm-3 at 80 cm from the discharge center. The discharge parameters and axial distance can be adjusted to achieve a low concentration of electrons and ions in the atmosphere, thereby effectively avoiding the etching effect caused by electron-ion collision and achieving a better modification effect.