Abstract: The nonlinear dynamic bifurcation behavior of a rigid Jeffcott rotor-non-circular bearing system was investigated in a wide rang of parameters based with the help of Runge-Kutta method,Poincaré map and frequency spectrum.The journal bearing oil film forces were obtained from database.The diagrams of bifurcation,time course,frequency spectrum,phase and Poincaré map diagrams with some typical system parameters were numerically worked out.The results show that there exist abundant nonlinear dynamic behaviors such as double-period bifurcation,Hopf bifurcation,jump phenomenon,K-T periodic solution,quasi-periodic and chaotic motions and so on.The database method can provide the journal bearing oil film forces accurately and effectively for nonlinear dynamic analysis of rotor-non-circular bearing system.