A kind of wireless ECG monitoring system with real-time detecting and alarm function is described in this paper. The system was designed using S3C2410 and based on Linux. The program can be divided into three parts: data acquisition and display, ECG analyzing, automatic alarm. This paper mostly introduces the program of ECG analyzing and automatic alarm. Experiment results indicate that the system can monitor the patient's ECG real-timely and can detect 5 kinds of arrhythmias. The system sends alarm information automatically through GPRS when ECG signal is abnormal.