An optical frequency comb generation scheme using time-to-frequency conversion and optical fiber-loop modulation is proposed and demonstrated experimentally. Flat-top optical pulse train from an intensity modulator is injected into a fiber loop, which includes a phase modulator and an amplifier and is cyclically modulated by the phase modulator, to generate abundant optical comb lines. A total of 110 comb lines with 3-dB spectral power variation and 10-GHz frequency spacing are obtained. The proposed scheme is relatively simple and uses only one intensity modulator and one phase modulator.