An automatic liquid stop bag with a bending portion comprises: two outer films, two inner films, a storage area, a discharge channel, a bent portion, an inlet, an outlet and a tear portion. The storage area is formed by coupling the two outer films by hot sealing. The two inner films are disposed between the two outer films and coupled the two inner films by heat sealing to form a discharge channel or the discharge channel is coupled to the two inner films by heat sealing and formed between the two inner films, and the internal sides of the two inner films are not coupled to form the inlet and outlet, and the tear portion is formed at an edge of the two inner films and the two outer films and separated from the two inner films to expose the outlet of the discharge channel.