The invention discloses a battery charging circuit which outputs step current. The circuit comprises an input voltage source, a capacitor, n inductors L1 to Ln, n switch tubes S1 to Sn and n diodes D1 to Dn. A three-phase Boost circuit is employed, through changing the frequency, duty cycle and phase of a control signal, the step charging current with adjustable output amplitude and frequency can be obtained. Compared with the existing charging mode, the step current charging mode is employed, the charging performance such as charging efficiency and battery temperature rise is improved with different degrees, the battery charging circuit can be applied to occasions of high frequency, high current and high power, the battery charging circuit can be used in a small-power charger and a large-power electric car and has a significant improvement effect in a fast charging occasion, and the application range of the battery charging circuit is more extensive.