Objective Based on the dummy model, this experiment studies the relationship between different backrest angles and neck injuries under the effect of horizontal negative acceleration (-Gx). Methods The dummy model was fixed on the base of the acceleration platform facing the orbital direction, and the backrest angle was set up to 17°, 22°, 30°. Each experimental group performed 10 repeated tests according to the same acceleration curve, compared the differences between the upper and lower acceleration of the cervical spine under the same -Gx conditions, and calculated the neck injury index. Results The time-acceleration curves of the upper and lower cervical spine on the anteroposterior and vertical directions have same shape with peak differences. In the anteroposterior (X axis), the acceleration peak of the 22° backrest angle experimental group was slightly higher than the acceleration peak of the other two backrest angle experimental groups, but in the vertical direction (Z axis), the acceleration peak of the 22° backrest experimental group was significantly lower than the acceleration peak of the other two backrest angle experimental groups. In the anteroposterior and vertical directions, the NICmax measured by the experimental group with a back angle of 22° was smaller than the NICmax measured by the experimental group with a back angle of 30° and 17°. Conclusion There is a nonlinear relationship between the backrest angle and the neck injury. The neck injury of the dummy model with the backrest angle of 22° is smallest under the action of -Gx in this experiment.