Objective To investigate the effect from helmet mass and deviation of mass center on neck muscle activity in military pilots. Methods Based on AnyBody software platform, a musculoskeletal model of head neck complex was established including C0, C1-C7, T1 and 136 muscles. Concentrated loads were applied to simulate the role of helmet. Strength from seven main muscle groups under different helmet mass, mass center and +Gz acceleration loads were simulated and calculated.Results When mass center of the helmet and the head coincided with each other, the muscle groups (such as semispinalis, levator scapulae, splenius capitis and cervicis) which took charge of extension were activated. Muscle strength increased with helmet mass linearly and +Gz acceleration loads would make this increase multiplied. Flexion muscle began to work when mass center of the helmet moved backward, so did the lateral bending muscles when mass center of helmet moved in the right-and-left direction. Conclusions Helmet mass and its center have an obvious influence on neck muscle activity in military pilots. The musculoskeletal model established in this paper can be used to calculate the change in muscle strength under different situations and conduct a quantitative analysis for helmet design and validation.