Partial discharge of air is an important factor causing insulation deterioration of high voltage electrical equipment. The emission spectrum information in air discharge has close relationship with the discharge characteristics. In this paper, the development process of air corona discharge was simulated by needle-plate electrode, and the emission spectra in 200~980 nm wavelength range of “ultraviolet-visible-near infrared” band were detected. The emission spectrum at the initial discharge stage is mainly composed of the band spectrum of nitrogen molecule N₂, which are the second positive band system (Second Positive System, SPS) and the first positive band system (First Positive System, FPS) of N₂ respectively. With the deepening of the discharge degree, the kinds of particles that undergo energy level transitions become more abundant, resulting in complex spectral lines that overlap with the band spectrum and the linear spectrum. Moreover, the spectral range is extended from 280~460 to 200~980 nm. When the discharge is at a critical breakdown, the intensity of the emission spectrum increases sharply, and the highest intensity values appear at 500.715 and 777.202 nm, respectively corresponding to the spectrum of nitrogen ions N⁺ and oxygen atoms O. Based on the air discharge mechanism, it is found that the dominant peaks or bands at the three stages of initial discharge, discharge deepening and critical breakdown are caused by the radiative transitions of N₂, NO, O and N⁺, which are determined by the discharge energy. The characteristic spectrum wavelengths at the three discharge stages are 336.907, 239.687 and 500.715 nm, respectively. At the initial discharge stage, the intensity at 336.907 nm is absolutely dominant, and the relative intensity at 239.687 and 500.715 nm is very small. When the discharge degree is deepened, the intensity at 239.687 nm is dominant, and the relative intensity at 500.715 nm is the smallest. At the critical breakdown stage, the strength at 500.715 nm is dominant, and the strength at 336.907 nm is the weakest. In the 200~980 nm spectrum range of air corona discharge, although the photon number of the ultraviolet band (UV), visible band and near infrared band increases with the increase of the applied voltage, the normalized photon number of each band show that with the deepening of the discharge degree, the photon proportion in the ultraviolet band decreases while increasing gradually in the visible band, and the change of photon ratio in near infrared band is relatively small. There are obvious differences in the relative photon number distribution in the “UV-visible-near infrared” bands at different discharge stages, which can reflect the development of the discharge.