Trajectory consistency test and design techniques for mortar shells were discussed; the referential design control method was researched. Based on projectiles & rockets trajectory consistency test principle and method, trajectory consistency design theory for mortar shells was described. Its essence is ensuring that the trajectory difference between two projectiles is less than the design control limits by exterior ballistics calculation. On the base of cross-validation method, design control and inspection processes were introduced specifically by a design example. The test results show that the design control method is effective and practical.