Embodiments of this application relate to the field of storage technologies, and disclose a data backup method and a terminal, to back up user data in a terminal when the terminal cannot be used. A specific solution is as follows: A terminal includes a first data partition, and the first data partition supports to start an operating system when the terminal is powered on. The terminal starts the operating system by using a second data partition after detecting a power-on failure of the terminal or detecting a preset operation of a user. The second data partition is a blank data partition. After the operating system is successfully started, the terminal transmits user data in the first data partition to a first storage medium. The first storage medium is located outside the terminal and is connected to the terminal.