The invention discloses a thin-wall cast-in-situ concrete 
enclosure structure and steel structure flexible connection and 
water stop treatment method, which comprises the following steps of: A, performing surface treatment on a steel structure; B, 
welding a 
water stop steel plate; C, manufacturing a waterproof rock 
wool plate; D, installing the waterproof rock 
wool plate; E, 
welding horizontal and vertical steel bars; and F, closing concrete. By the method, the crack spreading of a concrete 
enclosure structure is effectively controlled, the condition that the concrete 
enclosure structure is deformed and cracked and then leaked because the concrete enclosure structure and the steel structure have a large 
linear expansion coefficient difference due to temperature change is avoided by utilizing flexible connection and the 
water stop steel plate on the surface of the steel surface in a projection area of a cast-in-situ concrete enclosure structure arranged at a joint, and the problem thata flexible connection material is non-fireproof in the 
welding process is solved by adopting the waterproof rock 
wool plate which is a non-combustible material. In addition, the method is simple in construction, and safe and feasible, the contraction crack of the concrete enclosure structure can be effectively controlled, a seepage path is blocked, the 
crack resistance and seepage resistance of the joint are improved, and the service life of the concrete enclosure structure is greatly prolonged.