In order to explore the influence of different acceleration and deceleration forms on the bearing performance during acceleration and deceleration, an isothermal and mixed lubrication model for journal bearings was established. In this model, the fluid mechanics was solved by the Reynolds equation with mass conservation boundary condition, while the contact mechanics was predicted by Greenwood and Tripp (GT) contact model. By the developed model and using different functions of the shaft speed, the start-stop performances of the journal-bearing system under different acceleration scenarios were analyzed. The effects of working conditions, lubrication oil temperature, and bearing structure parameters on the start-stop performance of the journal-bearing system were studied. It was found that the larger starting acceleration can help the journal-bearing system enter the hydrodynamic lubrication faster in the acceleration phase. In the deceleration phase, slow deceleration helps the journal-bearing system maintain hydrodynamic lubrication for a longer time. The higher final speed, lower lubrication oil temperature, and lower bearing clearance can make the journal-bearing system have a better performance in the start-stop process.