A system and method for updating dirty data of designated raw device is applied in Linux system. A format of a command parameter for updating the dirty data of the designated raw device is determined, to obtain the command parameter with the correct format and transmit it into the Kernel of the Linux system. Then, a data structure of the designated raw device is sought based on the command parameter, to obtain a fast search tree of the designated raw device. Finally, all dirty data pages of the designated raw device are found by the fast search tree, and then are updated into a magnetic disk in a synchronous or asynchronous manner. Therefore, the dirty data of an individual raw device can be updated and written into the magnetic disk without interrupting the normal operation of the system, hereby ensuring secure, convenient, and highly efficient update of the dirty data.