The present invention discloses a control circuit of power supply with selectable current-limiting modes, wherein the control circuit which maintains the power-output circuit of the power supply within the energy-limiting standard is performed with automatic detection mode. In the present invention, a current-limiting set unit of the control circuit is coupled to the power-output circuit and provides a current-limiting set value according to power-output levels of the power-output circuit and outputs a current-limiting set signal to a current-limiting switch unit. The current-limiting set unit sets up switch junctions on the power-output levels of the power-output circuit, and the current-limiting switch unit receives the current-limiting set signal to determine the state of the switch junctions in order to provide current-limiting detect values of single set or multiple sets of power-output levels for the current-limiting set unit.