This paper proposes two new models to predict the adhesion-related failure for the scratch drive actuator (SDA). Both models, the normal model and the shear model, assume that the deformation of the SDA and the surface energy are the same along the width direction of the SDA. As a result, the SDA is simplified as a cantilever beam with support flexibility. Moreover, the shear model considers the shear deformation of the beam tip. Based on the models, the effects of the following parameters on the adhesion-related failure are studied: the energy of the adhesion per unit area, the bushing height, the support stiffness and the plate length. It is found that failure of the SDA can be reduced by decreasing the energy of the adhesion per unit area or the plate length, or increasing the bushing height or the support stiffness. Comparing the two new models, it is shown that for most regions of the SDA, both models predict almost identical results. However, in the region near the tip of the SDA, the shear model reveals a jump phenomenon or snap-off, which is not predicted by the normal model. This phenomenon indicates that under the critical conditions, the tip of the SDA may or may not stick to the substrate depending on the initial conditions. In conclusion, the two new models and simulation procedures provide a powerful tool for the optimal design and the performance improvement of the SDA.