In order to optimize the parameters of dielectric barrier-discharge plasmas, the emission spectrum of second transition line of oxygen and nitrogen under normal temperature and pressure was measured with a grating spectrometer. The results show that the intensity of the emission spectrum of the plasma increases with the voltage, and the best frequency range to generate the plasma spectrum is 39—41kHz. Meanwhile, the introduction of helium gas increases the intensity to a high extent. In combination with the theoretical analysis, the feasibility of spectral method in the study of dielectric barrier discharge plasma is verified.