Bootloader (boot loader) is an important part of linking up the operating system and hardware platform, and also important for embedded system of software development. This paper describes characteristics of a powerful, stable U-Boot program in the development of the current embedded systems and transplant process. It realizes functions like kernel and file system of yaffs download, and Linux boot. By using the corresponding commands to download the kernel, yaffs file system and boot Linux, it proves the U - Boot accurate.