Simulation of the dispersion-imbalanced nonlinear optical loop mirror′s transmission characteristics with different parameters is made. The physical mechanism of using dispersion-imbalanced nonlinear optical loop mirror to compress pulse in mode-locked fiber laser is analyzed theoretically. 11 ps stable mode-locked pulse train at 1566.65 nm with the modulation frequency of 9.998748700 GHz is obtained by using figure-eight actively-passively structure. Meanwhile, 2～3 harmonic mode-locked pulses with uniform amplitude are obtained at the modulation frequency of 9.995792825 GHz and 9.996778256 GHz respectively. It is demonstrated that dispersion-imbalanced nonlinear optical loop mirror can effectively eliminate the wings and noise of pulse to obtained pulse train with uniform amplitude.