To analysis the electromagnetic energy coupling way of gun-launched missile in flight state, the transmission line matrix (TLM) method was utilized to study the coupling effect of electromagnetic pulse in in-flight missile. The coupling law of electromagnetic pulse for missile was obtained by establishing the missile entity model and changing the incident angle and polarization direction of the electromagnetic pulse. The studies indicate that when the incident angle of the incident wave is vertical to missile center axis, the missile internal electric field strength amplitude produced by horizontal polarization wave is larger than what produced by vertical polarization wave and 45 °polarization wave, and the changes of incident direction have an obvious influence on missile internal coupling field.