The invention to a mountain tunnel lining waterproof layer construction device and a mountain tunnel lining waterproof layer construction method, which are used for paving and fixing non-woven geotechnical cloth and a waterproof coiled material on a mountain tunnel construction site conveniently and quickly. The method comprises the following steps: (1) paving the non-woven geotechnical cloth, namely, respectively fixing two rubber guide groove strips to surface of a tunnel wall which is subjected to primary lining along the circumferential direction by using expansion bolts; placing a plurality of roller sliding blocks in each guide groove; binding leading wires at the back of the non-woven geotechnical cloth to the sliding blocks on the two sides; dragging the non-woven geotechnical cloth from the bottom of the arch springing of a tunnel, and moving while binding the leading wires along the circumferential direction of the tunnel until the non-woven geotechnical cloth completely covers the tunnel wall; firmly fixing the non-woven geotechnical cloth to the tunnel wall along the longitudinal direction of the tunnel by using strip-shaped rubber strips and steel bolts, and shearing the leading wires which are bound to the sliding blocks; (2) paving the waterproof coiled material, namely, paving the waterproof coiled material according the same steps, and then fixing the waterproof coiled material to the rubber strips which are used for fixing the non-woven geotechnical cloth by a hot welding method.