To improve the concentration of projectiles, drag brake was used to realize the longitudinal range correction. Fluent was applied to analyze three grenades with three different head shapes. The simulation results were contrasted with wind tunnel experimental, and showed that the rule of drag coefficient was identical, the consistency was got and the legitimacy of the model and FLUENT software were checked by the simulation. Based on it, in order to get the corresponding resistance coefficient, drag brake of different setting position has influence in aerodynamic characteristics. The mathematical model of one dimensional trajectory of correctional projectile was built and ballistics calculation program was compiled by VC++6.0. The corresponding amount range correction was calculated and analyzed by producing ballistic program when drag brake acting in different position on trajectory.