A startup control method for a DC/DC converter is used for starting the DC/DC converter with energy transferred from a low-voltage side to a high-voltage side, and includes: determining a duty cycle or a frequency of a driving signal based on at least a voltage spike reference value and a voltage spike measurement value of a power switch at the low-voltage side; and outputting the driving signal to the power switch, thereby controlling the on and off of the power switch. The startup control method for a DC/DC converter of the disclosure can improve a reverse charging power of the converter to the maximum extent and reduce the time needed for charging a bus capacitor during a reverse startup process while ensuring voltage stress on the power switch not to exceed a limit.