A model to predict the shock response of a 1.8-inch hard disk drive (HDD) is developed and validated by experiment. The head-actuator assembly (HAA), spindle disk and flexible base are included in the proposed model. The feasibility of modeling the air bearing as linear springs is investigated for HDD operating shock simulation. Result shows that as far as the vibration of the arm-suspension assembly is concerned, the air bearing between the disk and slider can be modeled by linear springs to speed up the simulation. However, if head/disk interface is concerned, the air bearing should not be modeled as linear springs in the studies of head-disk interface.