A method and device for playing compressed multimedia files in a semi-power on state of a computer is provided. A program is provided in the BIOS so that POST (Power On Self Test) is not performed after the power is turned on. The program directly initializes multimedia chips or chipsets. A micro controller is provided as the interface for the CPU to control to execute the commands given by its user. Finally, the processed result is presented by a player. Through the simple method, the user can make the computer play compressed multimedia files directly, achieving the goal of a computer with the home electronics functions.