In pre-hospital emergency, it's essential to immediate recognize cardiac arrest, and use real-time ECG monitoring for patients. We propose a concept of whole-course ECG monitoring and implementation in pre-hospital emergency, and design a portable pre-hospital ECG monitor (Pre-ECG). There are two working modes in Pre-ECG, i.e., rapid detection and continuous monitoring modes. In rapid detection mode, ECG waves and heart rate of patients can be displayed in a few seconds by using metal electrodes, which helps to understand the status of patients' cardiac electrical activity.After connecting lead wire to the Pre-ECG, it can automatically switch to working in continous monitoring mode. At this time, ECG waves and heart rate can be displayed in real time, and give an alarm for abnormalities of heart rate, which can well meet the requirement from transfer process of patients. Moreover, all ECG data derived from the two modes can be stored permanently in TranFlash card, which can be printed via bluetooth printer, be used for remote medical consultation through the internet, or be reserved as legal evidence and academic research materials.