Digital clock is common and widly used in our daily life, Acoording to the disign requirments,LED digital circuit design should be used to scanning display hour, minute,second by six digital tube dynamic, in 24-hour time arctical content two main aspact,one is Hardware circuit design and the other one is software programming hardware circuit main include central processing unit circuit clocking circuit and software in assembly language, including the procedure, time setting subroutines software modules. Circuit can realize that time, adjust the time, save electricity state (digital tube not bright, clock keep) three functions meet the design requirement and purpose.