The diameter of the inlet of the Laval nozzle, the diameter of the throat, the diameter of the outlet of the nozzle, the length of the contraction section, and the length of the expansion section have certain effects on its atomization effect. In this paper, a dimensionless quantity method is used to simulate and study a variety of working conditions with three variables of throat diameter, nozzle inlet diameter, and contraction length in the Laval nozzle structure by Fluent to obtain the optimal structure of the Laval nozzle parameter.