A theoretical model of temporal coherent stacking of short pulse based on Gires-Tournois interferometer (GTI) has been established. The progress of coherent pulse stacking and its temporal evolution is simulated theoretically. The impact of amplitudes and phases in the pulse burst on the stacking shape and efficiency is simulated numerically and analyzed. Through the simulation and optimized design of the amplitudes and phases in the pulse burst, the peak amplification coefficients of three pulses and five pulses in the coherent stacking are approaching 2.479 and 4.43, and the energies in the main pulse are 96.9% and 95.1% respectively.