The invention relates to a building roof outdoor rain leakage preventing sunshade board system and particularly relates to a building roof outdoor rain leakage preventing sunshade board system provided with special-shaped elastic sealing strips. The technical scheme of the invention is as follows: a movable, openable and closable building roof outdoor rain leakage preventing sunshade board is provided, and when the outdoor rain leakage preventing sunshade board is opened, large area natural lighting and ventilation can be realized by adjusting the angle of blades; when the outdoor rain leakage preventing sunshade board is closed, sunlight can be completely obstructed in clear day, and in a rain day, even extraordinary rainstorm in the summer, rainwater can be smoothly drained off along a water drainage groove arranged in an outdoor rain leakage preventing sunshade board device; and interconnection parts among the blades are all provided with the special-shaped elastic sealing strips, so that spilling and leakage caused by rainstorm can be prevented effectively.