Abstract: A mathematical model of precise harmonic drives transmission system including the effects offriction and transmission flexibility is developed and identified experimentally. In our model, the characteristics ofthe harmonic transmission are expressed as a function, the frictions in both motor and load side are analysed,nonlinear friction is described as a function of position and velocity, the average friction is described by a secondorder polynomial, and the periodical part of friction is simulated by Fourier series. The consistency of simulationresults and experimental outcomes confirm the effectiveness of the proposed model.