A kind of pocket electrocardiograph was designed with simple circuit and small volume in this paper.It also explaind in detail how to sample the signal from a patient’s heart and stor it in the flash memory.Though the analysis to the theory and characteristics of micro one-wire linked electrocardiogragh,this paper puts forward the compersitionand foundermentals of all parts.The storage of mass data has been solved by using flash memory 29f040.AT89C51 is one kind of current ships of MCS51 series ,which are produced by ATMEL company.A new type of ECG analog amplifying circuit that constructed by integrated chips AD620AN and LM301AN has been designed.AD620AN is a kind of instrumention amplifier which has low power and high precision.It is one of the best chips which are usually used in for-adead amplifying circuit of ECG.This system uses the Microcontroller AT89C51 and LCD module FM12864J instead of the PC and displayer.The system has the following features,such as small size,real time display,safe,high sampling frequency,simple operation and cheapness.