Abstract: Embodiments of the present disclosure provides a mounting method and system of external storage device of a dual system, the dual system includings a first operating system and a second operating system. The mounting method includes: transmitting a mounting request to the second operating system through the first operating system when the external storage device is mounted on the second operating system; unmounting the external storage device that is mounted on the second operating system when the second operating system receives the mounting request; mounting the external storage device on the first operating system when the second operating system successfully unmounts the external storage device. In this way, operation steps of mounting the external storage device in the dual system are greatly simplified, so that it is convenient for users to utilize, and user experience is improved.