The invention discloses a rainwater inspection well cover mechanism for a drainage cover capable of being opened and closed automatically and belongs to the field of municipal drainage inspection well supporting facilities. The rainwater inspection well cover mechanism is composed of well covers, a water channel, water inlet pipes, self-filling-drainage opening/closing water bags and stress spring connection pieces. The upper-layer well cover is a grid through hole cover. The lower-layer well cover is composed of same unit cover bodies symmetric about the geometric center. The peripheries of all the unit cover bodies are connected with the water channel through hinges. The top end of an opening of the water channel is fixedly connected with the upper-layer well cover. The upper end faces and the lower end faces of all the unit cover bodies of the lower-layer well cover are correspondingly connected with the upper-layer well cover and the self-filling-drainage opening/closing water bags through the stress spring connection pieces respectively. The corresponding self-filling-drainage opening/closing water bags are filled with rainwater entering the water channel from upper-layer grid through holes through the corresponding water inlet pipes so that all the unit cover bodies of the lower-layer well cover can be automatically rotated downwards to drain away water, the road surface rainwater collection capacity of a rainwater pipe network system is improved, otherwise, on non-rainy days, all the unit cover bodies of the lower-layer well cover are closed automatically, and bad smell in a well is prevented from overflowing.