A debug device of embedded systems is provided. The embedded system includes an embedded processor for reading a bootloader from a flash memory through a data flash interface. The debug device includes a memory transmission interface, a dada storage module, a data control module and a display module. The memory transmission interface is configured to couple the data flash interface for receiving data to the data storage module. The data control module determines whether the data stored in the data storage module is data from a data bus or from the data flash interface according to whether a data control signal of the data flash interface has been triggered. The display module displays the data of the data storage module.