With the development of high-speed permanent magnet synchronous motors (PMSMs), the iron loss generated in the inverter-driven PMSM system is also increasing. As the iron loss of the PMSM system is influenced by the control strategy, inverter, and the motor itself, which interact with each other mutually and complicatedly, in conventional loss calculation methods they are not considered synthetically. This paper proposes a strategy-circuit-field co-simulation methodology, which can take into account the mutual influence of control strategy, inverter, and motor. A hysteresis-based iron loss calculation method is introduced and utilized to further improve the loss calculation accuracy. The co-simulation results show that the proposed method can reflect the behavior of the PMSM system more physically, and mutual influence between the three aspects can be presented. Finally, the corresponding experiments are conducted, and the results are compared with the simulation results, proving the proposed methodology’s feasibility and effectiveness.