Background <p>Local defects often occur in the bearing raceway and affect the bearing service performance.</p> Purpose <p>The rectangular defect usually represents the spall shape in many works, and simplified displacement functions are used to simulate additional deformation in the spall area. However, this displacement function did not establish the relationship between the rolling element and spall profile, and the existing defective bearing dynamic models mainly operated at constant speed.</p> Methods <p>This study proposes a general time-varying additional displacement function related to the irregular spall profile, and the ball bearing dynamic model under speed fluctuation conditions is developed.</p> Results <p>The accuracy of the proposed model is verified by comparing the results of the experiment and two widely used models. Then, the effect of spall size, profile shape and speed fluctuation on the vibration acceleration is discussed. The results indicate that spall size significantly affects the vibration acceleration of two spall types, while the profile shape does not. Speed fluctuation will affect the impact acceleration amplitude of two spall types in different directions.</p> Conclusions <p>The proposed modeling method can more accurately describe the vibration state of bearings with defects and facilitate equipment monitoring.</p>