The invention relates to the technical field of hydraulic turbines, in particular to a method of measuring the amount of lubricating oil of a water guide bearing of a hydraulic turbine set. According to the method provided by the invention, a direct-flow transducer and an adverse-flow transducer are involved; the two transducers are respectively mounted on the two sides of a fluid pipeline at a certain interval; the inside diameter of the pipeline is D; the traveling path length of ultrasonic waves is L; the direct-flow speed of the ultrasonic waves is td; the adverse-flow speed of the ultrasonic waves is tu; the included angle of the propagation speed of the ultrasonic waves and the flow direction of a fluid is theta. Through the method, the flow rate is measured, and the flow rate can be calculated through a mathematical method. The method disclosed by the invention has the advantages of high flow measurement precision and convenience in installation; online measurement can be performed, so that the test workload can be reduced effectively and the test cost can be reduced. Through the method disclosed by the invention, the problem that the measurement of the flow rate of the lubricating oil of the water guide bearing of the hydraulic turbine set is inaccurate can be solved, so that the service life of the hydraulic turbine set can be prolonged effectively; the work efficiency of the hydraulic turbine set is improved; the safety of the hydraulic turbine set is improved.