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 and a 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 and provided 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.