Key techniques were proposed in printout electrocardiogram (ECG) digitalization, which were composed by image edge detecting, angle adjusting, and ECG waveform extracting, de-noising, scaling, and saving. The requirements of digitalizing procedure contained ECG amplitude accuracy rate, heart rate counting, and morph changes. Experiments showed that the key techniques can preserve the fatal features and parameters efficiently, precisely, and automatically. The accuracy rate of waveform amplitude reaches 95%, and heart rate of that reaches 98%. The results satisfied the clinical requirements, and can be used for network medical service.