The water production mechanism of thermal recovery horizontal wells is complicated，and detect the water breakthrough point is the key to efficient water blocking. At present，the common water detection methods have difficulty in raising and lowering the instrument and high cost of dynamic test in oil well. Therefore，this paper proposes an analysis method of the wellbore temperature profile to detect the water breakthrough point of thermal recovery horizontal wells. According to the theory of heat conduction and multiphase pipe flow，under the condition of oil-water two-phase flow in the wellbore，we analyze the heat convection and heat conduction at the wellbore，the Joule-Thomson effect，the temperature change of the wellbore induced by the work of gravity，and the pressure drop of the wellbore caused by the joint work of gravity and shear.Then we construct a calculation model of wellbore temperature of thermal recovery horizontal wells during production，obtaining the wellbore temperature profile of the horizontal wells. Since the water production from the horizontal section during production will cause abnormal fluid temperature in this interval，the water breakthrough point can be determined by comparing the difference between the theoretical profile and the measured temperature curve. Then the source of the produced water can be analyzed according to the temperature.