Back to back start-up is currently the key backup start-up method for pumped storage units in the pumping direction. This article starts with the process of back-to-back starting and analyzes and summarizes the main factors that affect the success of back-to-back starting by sorting out the physical process of the starting process. Based on the back-to-back start-up test of a 300MW pumped storage power station, suggestions were made for the opening law of the driving guide vanes and the selection of excitation currents for the driving and driven machines by comparing different excitation systems and governor parameters. Meanwhile, based on the experimental conditions, the back-to-back starting process was analyzed from the perspective of rotor position. The optimized parameters successfully enabled the driven unit to reach the rated speed and synchronize with the power grid, improving the success rate, reliability, and stability of the back-to-back start-up method for the power station.