Octagon structure consisting of the spots and lines was firstly observed in discharge in argon and air mixture by using a dielectric barrier discharge device with water electrodes. Plasma temperatures of the spots and lines in octagon structure at different gas pressure were studied by using optical emission spectra. The emission spectra of the N2 second positive band(C3Πu→B3Πg)were measured, and the molecule vibrational temperatures of the spots and lines were calculated by the emission intensities. Based on the relative intensity of the line at 391.4 nm and the N2 line at 394.1 nm, the average electron energy of the spots and lines were investigated. The spectral lines of Ar Ⅰ 763.26 nm (2P6→1S5) and 772.13 nm (2P2→1S3) were chosen to estimate electron excitation temperature of the spots and lines by the relative intensity ratio method. The molecule vibrational temperature, average electron energy, and electron excitation temperature of the lines are higher than those of the spots at the same pressure. The molecule vibrational temperature, average electron energy, and electron excitation temperature of the spots and lines decrease with pressure increasing from 40 to 60 kPa.