A DC power supply for preventing output from being misconnected to a power supply and its LED lamp and control system, comprise a DC power supply and an anti-misconnection module. The DC power supply comprises a positive output terminal and a negative output terminal. The anti-misconnection module comprises a positive access terminal and a negative access terminal which are electrically connected to the positive and negative output terminals of the DC power supply respectively, a NMOS transistor controlling on-off of the negative access terminal, a load access unit performing a turn-on operation of the NMOS transistor, a forward-blocking unit performing a turn-off operation of the NMOS transistor, and a backward access unit performing a turn-off operation of the NMOS transistor. The present invention prevents the DC power supply from being damaged even if the positive access terminal and the negative access terminal of the DC power supply are mis-connected to the external power supply, such as the electric supply or the dry battery. As long as the external power supply is removed and the normal load is connected, such as LED lamps, the DC power supply of the present invention can work normally, so that it can not only improve the reliability of power supply products, but also can reduce the corresponding maintenance workload.