Industrial continuous inkjet printers are typically used in production lines for printing directly on various types of products such as cans, bottles, and packages. To enable their application to higher speed production lines, their print quality needs to be improved. Print distortion results from aerodynamic and electric interference among the ink particles during their flight from the nozzle to the print target. An ink-particle flight simulation method that enables the trajectories of ink particles and the airflow around them to be calculated simultaneously has been developed for use in identifying the mechanism of print distortion. Simulated printing of multiple-dot lines revealed that the lines were distorted when they hit the print target. 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.