A portable infusion monitoring system detects the liquid level and flow rate during infusion process, as well as gives an alarm for patents and nurses in hospital as the medical liquid in an IV bottle drops to a predetermined low level. This system comprises a set of liquid level sensor, a microprocessor, and a monitor terminal. The liquid level sensor generates an electric signal related to the liquid level inside the IV bottle. The microprocessor statistically analyzes the electric parameters detected from the electric signal, and obtains the liquid level data including both the liquid level and liquid flow rate. The liquid level data are sent to the monitor terminal for display, and an alarm is activated when the medical liquid inside the IV bottle drops to a predetermined low lever. Further functions of the monitor terminal includes an automatic switch to cut off the IV feeding process and send the alarm signal to a nurse station through signal network by wire or wirelessly. Several interference filtering methods are applied to increase signal/noise ratio, and therefore warrant the operation reliability.