An objective characterization method for lighting flicker based on frequency spectrum analysis is proposed. Time-varying light signals were Fourier transformed into frequency domain, filtered by bandpass filter that matched Contrast Sensitivity Function (CSF), and applied inverse Fourier transform into time domain again. Based on the modulated transient light waveform, Flicker Degree (FD) was defined as a measure of lighting flicker. Several kinds of typical illuminants were tested and their FDs were calculated. Results agreed well with previous experiment and showed more stable repeatability. The method combined with human visual system provides an objective evaluation for lighting flicker, and gives a hand with lighting optimization design and industrial standardization.