Impact features caused by the bearing defects can be used to detect the defect sizes. The current defective vibration models for ball bearings only considered the effect of defect length. The effects of the defect width, defect depth, and ball-raceway contact deformations are ignored to simplify the vibration models. Meanwhile, the impact forces and processing when the balls pass through the defect are not accurately calculated. However, those above factors have a great effect on the impact features. To overcome those issues, a new impact model of a deep groove ball (DGB) bearing with a defect based on the previous model is established by using the exponential and trigonometric functions. Based on the collision and geometry models in the previous works, the effects of the defect width, defect depth and ball-raceway contact deformation are considered. The proposed impact model can accurately simulate the actual vibration signal of defective ball bearings. It can be used to detect the defect sizes. The impact positions when the balls entering the defect of outer ring are calculated. The abnormal changes in the bearing vibrations are analyzed. The results can provide useful references for understanding the impact features excited by the bearing defects.