To study the dropping damage evaluating method of product packaging system with a cantilever beam critical part and provide theoretical directions for the packaging design of similar products. A nonlinear dropping shock dynamics model was established for the packaging system. Dropping damage boundary curve for the cantilever beam critical part was created by the modal superposition method with inner stress as evaluation indicator and system parameter and speed variation as variables. Example showed that the safety area of the system decreased as the concentrated mass and the frequency of main component increased. And the system safety performance would be better if the allowable stress was higher. In conclusion, for the nonlinear packaging system with a cantilever beam critical part, concentrated mass and frequency of main component have a significant impact on the dropping safety area.