The novelty of this paper is to explore the tribo-dynamic behavior during start-up for microgroove bearings under impact loads considering manufacturing errors and unbalanced rotors. Based on the average flow equation, the film thickness equation with various surface profiles, the asperity contact model, the acceleration model and the rotor dynamic equation, a mixed lubrication model for the bearing during start-up has been developed. The validity of the proposed model is verified by comparison with the reported results. The effects of acceleration modes, boundary conditions, unbalanced loads, impact loads, manufacturing errors, and microgroove surfaces on the tribo-dynamic behavior of the bearing during start-up are evaluated. The simulation results demonstrate that the reverse S-shaped acceleration model accelerates the formation of the hydrodynamic effect, shortens the contact time, and reduces the contact loss. The cavitation effect on the peaks of the maximum fluid and contact pressures differs significantly at the start-up stage under the Reynolds and JFO boundary conditions. The unbalanced and impact loads cause fluctuations in the shaft centre orbit, and these effects increase in magnitude. The parametric analyses show that the manufacturing errors significantly affect the hydrodynamic effect and the contact time, with the impact relating to the error type. Furthermore, the microgroove surface plays an important role in the tribo-dynamic behavior of the bearing.