To study the effect of transversely excited atmospheric (TEA) CO2 laser pulse waveform on the momentum coupling coefficient, the waveform of laser pulse was changed, and the pulse duration was compressed about to 50% by controlling the pressure of the gas and proportion of components in gas mixture. According to that, some experiments and numerical calculation were done. Achieved results indicate that increasing the coupling coefficient is very favorable for decreasing the proportion of energy between the forepart and the whole pulse in TEA CO2 laser propulsion. Also, the coupling coefficient can be effectively raised while pulse duration is bigger than characteristic time of two-dimensional movement.