The electric compound turbocharger which integrated a high speed motor into a turbocharger rotor shaft can be used transiently to accelerate the turbocharger more quickly in response to an acceleration requirement. It can utilize the exhaust gas energy fully to improve the engine fuel efficiency and benefit for engine lower emissions. The key technique for electric compound turbocharger is to solve the reliability problems when an electrical motor integrated into a turbocharger shaft between the turbine and compressor wheels will increase the burden for the bearing support and affect the turbocharger shaft rotation characteristics. In order to know the dynamics behavior of higher load bearing system is explored for reliability, this paper is focus on the nonlinear rotor dynamics characteristics of electric assisted compound turbocharger rotor bearing system. Based on the principle and structure of electric compound turbocharging rotor bearing system, the basic theory method and dynamics model of rotor bearing system considering the nonlinear oil film force is established. The shaft critical speed, unbalance response, stability performance are analyzed, the nonlinear oil film vortex and the oil film oscillation analysis shows a complex rotor dynamic behavior of electric compound turbocharger. The influence on the key structural parameters and oil film clearance for rotor bearing system is discussed. The nonlinear rotor vibration characteristics of electric compound turbocharger under actual operating conditions are predicted. The results can support a theoretical basis for the design of nonlinear shafting dynamics of electric compound turbocharger and increase rotor bearing system reliability for future products.