The invention discloses a high-flatness integrative solar power generation integral roof and an installation method thereof, which solve the technical problems of complicated structure, high cost and unscientific installation of the prior solar power generation roof. The high-flatness integrative solar power generation integral roof comprises solar power battery components (1), U-shaped steel drainage channels (3), roof purlins and a roof upright post. The installation method comprises the following steps that: the U-shaped steel drainage channels (3) used as rafters are parallelly and fixedly arranged on a first purlin (4)and a second purlin (5) of the roof at intervals; the solar power battery components (1) are arranged between lateral plates of the adjacent U-shaped steel drainage channels (3); the outer side edge of an aluminum-type frame (9) arranged at the lower end of each solar power battery component (1) is provided with a tail edge (2) in a extension mode; the tail edge is overlapped on the edge of the upper end of a solar power battery component arranged below the tail edge, and sealing strips (11) and (15) are additionally arranged on the edge of the upper end to formvertical connection; and the connection is sequentially installed by rows from left to right along the slope roof to obtain the high-flatness integrative solar power generation integral roof. The high-flatness integrative solar power generation integral roof realizes the perfect combination of the flatness and the integration with buildings of the height of the solar power generation roof.