In allusion to the specific features of a non-linear rolling element bearing-rotor system with pedestal looseness at one support, The dynamical equations of roll element bearing - rotor system are derived using the theories of Hertz theory，non-linear dynamics and rotor dynamics after the nonlinear condition of looseness is taken into account. After simulating the dynamic equation of the system numerically, the complex motions including the period doubling and chaotic motions and the transformational laws are showed with the increase of the rotating speed and the augment of the clearance by means of the phase maps, the bifurcate maps, the Poincaré maps and the correlation dimension. The bifurcation, chaotic motions and their laws of changes roll element bearing - rotor system with pedestal looseness are analyzed based that. The valuable conclusions for engineering are acquired. The analysis results in this paper provide some reference for diagnosing the fault of Pedestal looseness.