A connecting fitting includes a body having a cam surface and an inserting assembly which is pivotally connected with the body. The inserting assembly includes an inserting member and at least one expandable member mounted between the body and the inserting member. The expandable member includes an expandable portion and a lip portion extending from the expandable portion. A compressible space is defined by the expandable portion and the lip portion, and the expandable portion has a plurality of snap portions. When the body is axially turned relative to the inserting assembly at a certain angle to generate a push force, the snap portions will be expanded outwardly by the push force.