Abstract: As one of the canonical flow problems in wall-bounded turbulence with system rotation, spanwise rotating plane Couette flow (RPCF) has been studied a lot in the past decades to investigate the rotation effect on the turbulent statistics and flow structures. Recently, the author and his collaborators had performed a series of direct numerical simulations on this flow problem. The results showed that the strong rotation and weak rotation have different impact on the flow structures and turbulent statistics. Furthermore, they have found that multiple states do exist in RPCF. That is, at the same control parameters (Reynolds number and Rotation number), the flow could be at two different flow states, and the flow structures and turbulent statistics at these two states show obvious differences. Their simulation results also showed that the multiple states could exist over a wide rotation number range. Further analysis on the role of secondary flows showed that the secondary flows play different roles in the energy transfer at different states. If the secondary flows are very strong, most of the energy from the mean field will first transfer to the secondary flow and then transfer to the residual field, and the secondary flows acts as a kinetic energy bridge that transfers the energy from the mean field to the residual field. On the other hand, if the secondary flows are not strong enough, most of the kinetic energy will transfer from the mean field to the residual field directly. The present results support the previous conjecture that the large-scale flow structures (the secondary flows) play a very critical role at the multiple states.