The invention discloses a thin-type LED lamp structure which comprises a seat body, a cover body, a cooling board, an LED module, a circuit board and a light-guiding hood. The seat body and the cover body are respectively provided with a seat body opening and a cover body opening; a waterproof outer wall and a waterproof inner wall enclosing the seat body opening and the cover body opening are formed between the seat body and the cover body by a tenon-and-mortise joint design; the light-guiding hood, the circuit board and the LED module are arranged in the waterproof inner wall and achieve the dual-waterproof efficacy by the waterproof inner wall and the waterproof outer wall; the tenon-and-mortise joint design by which the seat body and the cover body are constructed as a column body anda hole body also has the waterproof efficacy; a high-brightness LED is used in the LED module and cooled by the cooling board, and the cooling board is arranged on the outer side of the seat body andprovided with a plurality of convection cavities capable of achieving heat convection effect so as to improve the cooling effect and be miniaturized; and the upper waterproof wall and the lower waterproof wall with the waterproof efficacy are respectively formed between the light-guiding hood and the cover body and between the cooling board and the seat board by the tenon-and-mortise joint design.