Industrial continuous inkjet printers typically are used for printing directly on various types of products such as cans, bottles, and food packaging in production lines. Their application to 3D printing (additive manufacturing) also has recently become a promising area of research. To enable their application to higher speed production lines, their print quality needs to be improved. This means that ink-particle flight simulation technology is needed to clarify the factors that affect print quality. Print distortion results from aerodynamic and electric interference among the inkparticles during their flight from the nozzle onto the print target. A simulation technique has been developed that enables the trajectories of the ink particles and the airflow around them to be calculated simultaneously. The functions needed to accomplish this, such as calculation of the electrostatic force, the Coulomb force, and the aerodynamic drag force for many flying ink particles were added to a Lagrangian method used for fluid dynamic analysis. The simulated velocities and positions of the flying ink particles agreed well with the experimental ones and helped clarify the factors affecting print quality. Simulated printing of multiple-dot lines revealed that the lines on the print target were distorted. This was because the trajectories of the charged particles in the lines were distorted by electric and aerodynamic interference during flight. Simulation showed that the appropriate insertion of dummy particles reduces the print distortion in computers.