The invention relates to a stem flow intercepting method comprising the following steps of: firstly forming a waterproof layer, winding plastic cloth on the smooth position of a stem with a tree bark removed, then winding a folded elastic membrane on the upper end of the smooth stem and outside the plastic cloth, and then tightening by using iron wires; secondly downwards rolling the upper edge of the plastic cloth to wrap the elastic membrane, and tightening by using the iron wires; thirdly forming a waterproof plastic bib, upwards rolling the lower edge of the plastic cloth so that the smooth stem with the tree bark removed is wrapped in the rolled lower edge, and tightening by using the iron wires; and finally fixing a conduit for guiding water flows on the lower edge of the formed waterproof plastic bib so that the water flows are guided to a measuring device. The stem flow intercepting method can be used for intercepting 95-98 percent of stem flows, is convenient to implement without any influence on water quality and meets the requirements for water quality measurement of the water yield of the stem flows.