A DC power conversion circuit with constant current output includes a DC voltage source, a driving circuit and a control signal generator. The DC voltage source is used for providing DC power. The driving circuit includes a switch, a resistor, a diode, and an inductor. The switch has three ends, one used for receiving a control signal. Furthermore, the switch is used for conducting or cutting off a coupling between the other two ends according to the control signal. The resistor is coupled between the switch and a first grounding end. The diode has a first end and a second end coupled to a second grounding end. The inductor has a first end coupled to the first grounding end, and a second end coupled to a load circuit. The control signal generator generates the control signal for the second end of the switch according to a current of the resistor.