The invention discloses a round arch-shaped smoke discharging skylight structure with a water drainage system. The round arch-shaped smoke discharging skylight structure comprises a round arc-shaped aluminum alloy sectional material which is used for installing a lighting skylight and is arranged on a skylight base, wherein water drainage grooves used for water drainage are respectively formed inconnecting positions of the middle part of the round arc-shaped aluminum alloy sectional material and lighting hollow plates arranged at the two side edges; the lighting hollow plates arranged at thetwo sides of the water discharging grooves are pressed and mounted onto the water discharging grooves through aluminum alloy press strips; in addition, fixing plates in separated arrangement are respectively arranged in the water drainage grooves; the aluminum press strips are fixed on the fixing plate through fixing elements; the edge position of the lighting hollow plate is pressed and mounted onto the skylight base through an aluminum alloy press plate; the outer side of the hollow plate of the skylight window is hinged onto the round arc-shaped aluminum alloy sectional material through a hinge; the opening is respectively opened by a motor arranged at the other side. The feasibility and convenience are provided for the subsequent sunlight plate replacement; glue is not coated; the repair problem and hidden danger caused by aging are prevented; the integral intensity of the skylight is enhanced; the processing of the whole structure is convenient; the appearance is attractive.