The paper reviewed the development and application of sap flow gauge. There are four different principles of sap flow gauge to measure sap flow rate of plants which are heat pulse velocity method, stem heat balance method, thermal dissipation method and laser heat pulse method. By information searching in SCI database and national knowledge infrastructure database of China, the paper made a summary about the application of sap flow gauge. Based on the analysis for research results and application progress, the stem heat balance and the thermal dissipation method will become the important measuring methods in the near future. While in view of the superiority of laser heat pulse method, it will heve a good prospect in the future.