In conventional rational harmonic mode-locking, optical pulse trains with the repetition rate of (pn 1)f_(c) are generated when the modulation frequency of the in-cavity modulator is set at f_(m)=(n 1/p)f_(c), where n and p are both integers, f_(c) is the fundamental cavity frequency. In this paper, we report that rational harmonic mode locking phenomenon takes place in the fiber lasers when the modulation frequency is set at f_(m)=(n 2/p)f_(c). The pulse generations are experimentally demonstrated when the numerator of the rational corresponds to 2 in 5th and 7th order rational harmonic mode-locking.