Objective To investigate the formation processes of droplet in a piezoelectric system. Methods The system simulated the droplet formation and ejection of a piezoelectric inkjet printing device based on VOF method under the condition of a given pressure. The effects of ink physical properties (including surface tension and viscosity) on the ejection behavior of droplet were presented. Results The typical moment of the formation process was given. The proper parameters to get ideal monodisperse droplet were determined. The proper surface tension was 40 mN/m and the viscosity was 10 Pa· s, which meant that Z was 4.86. Conclusion The conditions to get the ideal droplet form were validated by the experimental observation, which proved that the simulation was reliable.