The pulse-stacking technology is one of the schemes of generating arbitrary seed pulse in the high power laser system which is used to spread the broadband short pulse to satisfy the need of the pulse-stacking components due to the wideband character of the large chirped fiber Bragg grating (LCBG).The reflect spectrum and the time delay of LCBG were simulated through the transmission matrix method.As a result,the dispersion and bandwidth depend on the chirp factor of LCBG,but the cost to increase the dispersion is the reduced bandwidth.The results also show that the bandwidth would be increased remarkably with longer LCBG,but at the same time the dispersion was invariable.These results are significant for designing the front-end of the high power laser system.