The invention discloses a method for lifting and installing a whole bridge arch rib. The method includes the following steps of dividing the arch rib into two side arch rib bodies and a middle arch rib body, splicing the side arch rib bodies on a wharf, hoisting the side arch rib bodies to a set position through a floating hoist, erecting a side supporting system and a lifting portal, installing a lifting system, splicing a middle supporting system below the design position of the middle arch rib body, installing the middle arch rib on the upper face of the middle supporting system, arranging a temporary beam at the bottom of an arch foot of the middle arch rib body, arranging a temporary horizontal rope between the two ends of the arch foot, correspondingly connecting the lifting system with the temporary beam, and lifting, horizontally moving, putting down, putting in position, folding and installing the whole middle arch rib body. By means of the method, the requirements for installation quality and precision of the large-span arch rib bridge can be met, section lengths can be flexibly adjusted, section manufacturing quality is optimized, and section in-situ precision is improved.