Abstract: Pulse modulation radio-frequency（RF） has lots of adjustable parameters（modulation frequency, duty cycle,input power and so on）, which can regulate plasma parameters at a large scope. Compared to AC or DC discharge, RF discharge has its distinctive features. This paper presented experimental study on optical properties of Ar/CO₂ discharge driven by a 13.56 MHz RF power system at atmospheric pressure, and the main task was to investigate the influences of modulation parameters and gas composition on plasma plumes,optical emission spectrum（OES） intensity and electron excitation temperature. The results show that changing the RF modulation parameters can significantly regulate the optical properties: increasing the input power and duty cycle, or decreasing the modulation frequency and CO₂ content can increase the plasma plume length and electron excitation temperature. Main feature spectra are OH（A→X）, N2（C→B）,Ar（4 p→4 s）, O（3 p→3 s）, C（1 p-1 s）, C2 swan and so on, and their intensities are obviously enhanced with the increase of input power and the decrease of CO₂ content. This study provides more options for RF discharge plasma technology to improve CO₂ utilization efficiency.