Based on the classical Bertotti trinomial constant coefficient iron loss calculation model and the harmonic analysis principle, a high density permanent magnet synchronous motor (PMSM) iron loss calculation model considering eddy current loss, hysteresis loss and additional loss compensation coefficient was proposed. The compensation coefficients in the model varied with the amplitude, frequency and distortion rate of magnetic density, which could better reflect the effect of fundamental wave and harmonic magnetic field on iron loss. In order to verify the validity and accuracy of this model, two PMSMs with respectively 48 slots/8 poles inner rotor and 36 slots/48 poles outer rotor were taken as examples to compare the calculated value of the model with the finite element simulation results and experimental data. The results showed that the iron loss calculation model proposed had higher accuracy, and was suitable for applications in a wide range of magnetic density amplitude and frequency especially.