A detection circuit is used to detect an input current of a switching power conversion circuit. The current detection circuit includes a current transform unit, a first unidirectional conduction component assembly, a flux reset circuit, a second unidirectional conduction component assembly, a first switch, a second switch, a control unit, and a detection unit. The current transform unit is coupled to a power switch of the switching power conversion circuit, and the first unidirectional conduction component assembly, the flux reset circuit, and the second unidirectional conduction component assembly are connected in parallel to the current transform unit. The first switch and the second switch are coupled to the first or second unidirectional conduction component assembly, and the control unit correspondingly controls the first switch and the second switch according to a first or second direction voltage of the input voltage.