A method and terminal for starting a USB state machine are provided in the present document. The method includes: connecting a USB voltage bus pin to a logic level; if detecting that a voltage of a charging voltage pin is greater than a threshold limit value, starting a charging state machine and the USB state machine. In the present document, the USB state machine is started through a signal for detecting plug-in and pull-out of a charger, which can not only trigger the start-up of the USB state machine, but also possess a function of satisfying overvoltage protection, thereby the charger and the USB are enabled to share one physical interface with the simplest and securest method under the premise of guaranteeing the reliability.