The design principle of a multi-parameter monitoring system is introduced in this paper. The system can monitor ECG, respiration, body temperature, non-invasive blood pressure, oxygen satur ation and pulse rate simultaneously. Large screen LCD is used in the system to display waves and data. Modular design was adopted with samll size,light weight and low power consumption. This system has DSP function and can store,playback, print data and can be networked with other system.