The basic principle of the optical fiber pulse stacker in Inertial Confinement usion(ICF) front end system is described. When the seed pulse is split,time delayed,amplitude modulated and combined in the stacker,last arbitrary shape pulse is shaped. The effect of the seed pulse shape,the time delay and phase difference between pulses and optical filtering on stacking pulse shape is analyzed through numerical simulation. The results show that the shaping pulse with less than 100 ps rising edge,less than 5% pulse fluctuation,100 ps time precision can be obtained through increasing rising edge and falling edge,controlling phase difference at π/2 between adjacent pulse and filtering output pulse. The performance index can satisfy the application of ICF.