The flight ballistic of the EML (electromagnetic launch) projectile was simulated. Based on the establishment of a rigid body six degree of freedom flight external ballistic model, the time-frequency analysis and eddy current analysis method were adopted to establish the EMdynamic coupling model for the analysis of muzzle disturbance caused by the interior vibration, and the dynamic grid technology was used to establish the EM-aerodynamic coupling model for the analysis of aerodynamic disturbance brought by sabot discard. Thereby, the flight trajectory model of EML projectile was obtained. Taking the IAT-HVP designed by the advanced technology research institute of University of Texas as an example, the influence of the muzzle disturbance on the velocity and aerodynamic characteristics of the projectile was simulated and analyzed when the projectile leaves the muzzle at 1117 m/s with 0° angle of fire, and the 200 m exterior trajectory of the projectile was obtained. Simulation results show that 24% deviation of the drop point relative to idea ballistic are caused by the disturbance of the integrated projectile in the muzzle, in which the maximum is caused by the muzzle vibration, and secondly the sabot discard.