The dc and 100 kHz low pressure discharges in acetylene-nitrogen mixture have been studied here. Optical emission spectroscopy was used for identification of active plasma components and to determine plasma temperature. Relative concentrations of H, CH and CN were investigated versus experimental conditions by optical actinometry techniques. Emission intensities of N2 and N$_2^+$ normalized to intensity of argon line were also monitored as a function of experimental parameters. The rotational temperatures from the N$_2^+$ B$^2\Sigma_{\rm u}^+$-X$^2\Sigma_{\rm g}^+$ (0-0) and CN B2Σ+-X2Σ+ (0-0) bands and vibrational temperatures from the CN (B2Σ+-X2Σ+) and N2 (C$^3\Pi_{\rm u}$-B$^3\Pi_{\rm g}$) spectra were determined. Plasma processes and plasma equilibrium state were discussed.