The dependence of the temporal wave-form and frequency spectrum of the broad-band laser pulse stacked by chirped pulses on the parameters of the sub-pulses is investigated theoretically and numerically.It is shown that,the temporal wave-form of the broad-band lasers stacked by the transform-limited pulses is usually smoothing,while that stacked by chirped pulses takes detrimental modulation.And the former consists of one spectrum line,while the latter consists of multiple spectrum lines.In addition,with the delay-time between neighboring sub-pulses increasing,the modulation riding on the broad-band laser pulse increases,and results in the spectrum lines of the output pulse to increase.The results can help in generating broad-band laser pulse of specific temporal wave-form and frequency spectrum by optimize parameters of the sub-pulses.