Based on the theoretical model of divided-pulse amplification, the effect of all parameters in the divided-pulse fiber amplification system with five-step birefringent crystals group cascading on the property of amplified picosecond pulse is numerically investigated. The results indicate that, the difference of nonlinear phase shift accumulation between divided pulses leads to the reduction of the combining efficiency. The optimal combining efficiency is obtained when the time separation between two adjacent divided pulses is larger than 2.5 times of pulse width. Under the condition of nonlinear coefficient and maximum gain of fiber amplifiers being fixed, the selection ranges of gain fiber length and seed pulse peak power are presented in order to obtain a transform-limited amplified pulse with an output peak power of 10 MW. Under the condition of fiber length being fixed, it is suggested to choose a seed pulse with low peak power and a fiber with large gain in order to suppress the impact of rotation angle bias and transmissivity on the property of the amplified pulse.