An LED underwater lamp comprises a housing (1) and an LED lamp body (2), wherein the housing (1) is fixed in a mounting hole of a mounting plate (20), an opening is provided at one end of the housing (1), the LED lamp body (2) is inserted through the opening and fastened within the housing (1), an inner water-proof sealing ring (3) is disposed between the LED lamp body (2) and the opening of the housing (1), an LED bulb (4) is disposed within the LED lamp body (1) situated at the opening of the housing (1), and a power line (5) extending to outside through the housing (1) is detachably connected to the other end of the LED lamp body (2).