The invention discloses an emergency traction power supply system of an electric motor unit, which comprises a traction transformer used for reducing high voltage of a contact network, two rectifiers used for rectifying alternating current of secondary side windings of the traction transformer into voltage of middle direct current links, two inverters used for taking electricity from the middle direct current links and performing inversion into three-phase alternating current, a two-way auxiliary current transformer used for taking electricity from the middle direct current links and performing inversion into three-phase alternating current or taking electricity from a two-way charger and then performing boosting and rectification into the voltage of the middle direct current links, an auxiliary load used for obtaining the three-phase alternating current from the two-way auxiliary current transformer or the two-way charger by an auxiliary load power supply busbar, and the two-way charger used for obtaining the three-phase alternating current from a three-phase alternating current output side of the two-way auxiliary current transformer and performing voltage reduction and rectification on the three-phase alternating current into direct current to supply power to a lithium titanate battery and a direct current load which are connected with the two-way charger, or used for taking electricity from the lithium titanate battery and performing boosting and inversion into the three-phase alternating current to supply power to the auxiliary current transformer.