Embodiments of the present application provide a method for charging a traction battery and a battery management system, which can improve the performance of a traction battery. The method for charging the traction battery is applied to a battery management system BMS of the traction battery, where the method includes: in a charging process of the traction battery, obtaining a state parameter of the traction battery, where the state parameter includes at least one of the following parameters: a state of charge SOC, a state of health SOH, and a temperature; determining an SOC interval value and a discharging parameter corresponding to discharging of the traction battery based on the state parameter of the traction battery, where the discharging parameter includes at least one of the following parameters: a discharging time, a discharging current, and a discharging waveform; and when the SOC of the traction battery changes by the SOC interval value, controlling the traction battery to discharge with the discharging parameter. Through this technical solution, the state parameter and the SOC of the traction battery are combined, to control discharging timing and the discharging parameter of the traction battery in the charging process. On the basis of ensuring the safety performance of the traction battery, the charging performance of the traction battery is improved.