The application of tracer technique to the measurement of the liquid flow rate of two-phase flow is tested. The principle of this method is as follows : A solution of a certain dye is introduced into the liquid continuously and next, at a far downstream distance, some additional fresh liquid is injected into the main flow. If the flow rate of this additional liquid is known, the rate of the main flow can be determined from the dye concentration in the liquid phase detected at the two positions, the upstream and downstream sections of the additional liquid injection. The results measured by this method agreed with true flow rates within ±6% regardless of flow pattern.