The fluid-solid coupling analysis of the nonlinear rotor-bearing system with labyrinth seal was presented. The dynamic equations of rotor-bearing system were built up by combining d’Alemdert principle with Rize way, then the nonlinear oil film forces based on steady short bearing model, unbalanced excitation forces and gas excitation forces calculated by FLUENT could be coupled to system. Such nonlinear equations were numerically solved by Newmark integration method. The dynamics and the representation characteristics were investigated through a lot of numerical calculations, then the occurrence and development mechanism of the different coupling faults revealed based on the results of numerical calculation. The severity and mutation of some faults were also studied.