Numerical simulations have been used to compare the transmission performance between low duty cycle RZ format with and without prechirping. It is shown that, pulse prechirping will act accompany with the second-order dispersion of the fiber and enhanced their effect to transmission performance. After slope compensation, prechirping of pulses is demonstrated to be helpful both in reducing pulse distortion and nonlinear interaction, and the transmission characteristic of the properly prechirped pulse with certain power level is better than that of non prechirping pulses. Moreover, the prechirping can be optimized to obtain the best transmission performance.