A nonlinear model of electromechanical governed system with multiple uncertain parameters and disturbances is established, and a backstepping nonlinear adaptive L2gain speed control (L2NASC) method with additional control variables and selfmodified parameters is proposed. By adopting KClass functions and additional control variables, the stable speed of the electromechanical governed system can be improved, and the γdissipation inequality can be disregarded in virtual function design. Comparing with the traditional speed control method, the backstepping L2NASC simulation results show that the response speed of the operating components, i.e., as control sleeve, etc., can be increased, the overshoot of the control output can be decreased and the stability of the speed control system can be enhanced.