Trichel pulse discharge is a common unstable phenomenon in the corona discharge. In order to further reveal the discharge mechanism and discharge characteristics of the Trichel pulse, the optical characteristics of Trichel pulse discharge are studied atapressure of 600Pa by using the needle plate discharge structure. At an average current of 20～300 μA, the discharge is divided into Trichel pulse discharge mode and normal glow discharge mode. In the Trichel pulse discharge mode, the average interelectrode voltage decreases with the increase of the average current. Under normal glow discharge mode, the average interelectrode voltage remains unchanged with the increase of average current. The luminescence images at different average currents are obtained. The region from the cathode needle tip to the anode plate is divided into negative glow region, Faraday dark region, positive column region, and anode glow region. With the increase of the average current, the luminescence in the negative glow region, the positive column region and the anode surface is significantly enhanced, the volume of the negative glow region remains unchanged, the length of the Faraday dark region gradually increases, and the length of the positive column region gradually decreases. When the Trichel pulse disappears, the luminescence in the negative glow region shrinks to the cathode tip, the positive column region shifts close to the anode plate, and the luminescence in these two regions is significantly enhanced. The emission spectra at different average currents are measured by an emission spectrometer in 300~800 nm. The emission spectrum intensity in the wavelength range of 300~450 nm is higher, the second positive band system (C3Πu→B3Πg) of nitrogen molecules and the first negative band system (B2Σ+u→X2Σ+g) of nitrogen molecular ions. The emission spectrum is weak near 650~800 nm, the first positive band emission spectrum of nitrogen molecules (B3Πg→A3Σ+u). According to N2 (C3Πu→B3Πg) spectra, the vibrational and rotational temperatures of nitrogen molecules at different average currents are obtained by fitting the emission spectra of the second positive band system. The results show that the molecular vibrational temperature and rotational temperature increase with the increase of average current. The molecular vibrational temperature is 3 900~4 500 K, and the molecular rotation temperature is 430~450 K. This paper calculates the electric field intensity at different average currents using the intensity ratio of nitrogen molecule ion line 391.4 nm and nitrogen molecule second positive band spectral line 394.2 nm. The results show that the electric field intensity increases with the increase of the average discharge current, in the range of 145~200 kV·m-1, which indicates that the electron energy increases with the increase of the average discharge current. When the Trichel pulse disappears, the molecular vibrational temperature and electric field intensity increase significantly, indicating that the electron energy and electron density near the tip of the needle increase.