The invention discloses a method of measuring friction stress on an interference surface of an
oil film. The method comprises the following specific steps: step 1, obtaining a variable relationship of a
viscosity coefficient [mu] of the
oil film when
time changes between a time t1 and a time t2, and measuring the thicknesses of the
oil film at the time t1 and the time t2; step 2, setting an initial friction stress t0, calculating a thin oil film equation according to the variable relationship of the
viscosity coefficient [mu] of the oil film when
time changes, the thickness of the oil film at the time t1 and a numerical value, and adopting explicit time-marching to arrive at the time t2, so as to calculate the thickness of the oil film at the time t2; step 3, comparing the thickness of the oil film calculated at the time t2 with the thickness of the oil film measured at the time t2, correcting the friction stress t0 according to a comparison result, and carrying out explicit time-marching to the time t2 from the beginning of the time t1 again, wherein the t0 is the solved friction stress t after the circulation when the thickness of the oil film calculated is consistent to the thickness of the oil film measured. According to the method provided by the invention, the friction stress on the interference surface of the oil film can be obtained.