。A non-linear dynamic model of a two-span elastic rotor-bearing system with coupling faults of pedestal looseness and rub-impact supported on three plain journal bearings was established. The complex motion characteristics of the rotor bearing system were studied numerically. The simulation results show that the unstable rotate speed of the rotor system with coupling faults is between the single fault of pedestal looseness and rub-impact. Within the sub-critical speed range, the chaotic region is increased firstly and than reduced gradually with the increase of the looseness mass. Within the super-critical speed range, the quasi-periodic motion disappears and the chaotic region is reduced gradually with the increase of the looseness mass, and the period-3 motion region appears obviously.