In this paper, we propose a novel photonic approach for generating arbitrary waveform. The approach is based on the property of real-time Fourier transform in the temporal Talbot effect, where the spectrum of the modulating analog signal is converted into the output time-domain waveform in each period. We present a concise and strict theoretical framework to reveal the relationship of real-time Fourier transform between the optical signals before and after the dispersion. A proof-of-concept experiment is implemented to validate the presented theoretical model. We propose to generate symmetrical or asymmetrical arbitrary waveforms by using double-sideband or single-sideband modulation, respectively, which is verified by simulation results. It is shown that the given approach can be used to generate a repetition-rate multiplied optical pulse train with arbitrary waveform by simply using a multi-tone RF signal with appropriate frequencies and powers.