The invention discloses a method for realizing online prediction of maximum permissible power of a lithium ion battery. The method comprises the steps of: establishing a battery physical model according to charging and discharging characteristics of the lithium ion battery, and calculating a state of charge and a polarization voltage of the battery; utilizing the battery physical model to calculate a difference value between a battery terminal voltage and a battery charge and discharge limiting voltage by taking the state of charge and the polarization voltage as initial conditions and takingbattery-permissible maximum transient charging and discharging current as an initial probe current; and acquiring an increment for adjusting the probe current according to the difference value betweenthe battery terminal voltage and the battery charge and discharge limiting voltage so as to obtain a new probe current, and calculating a terminal voltage of the battery circularly by means of the battery physical model until a condition of calculating maximum permissible charge and discharge power in a current operating state is satisfied, thereby realizing online real-time prediction of a maximum power state of the lithium ion battery. The method overcomes the difficulty that the maximum permissible charge and discharge power estimation is subject to coupling constraints of working conditions, temperature, state of charge, attenuation and the like, and guarantees the estimation precision.