Abstract: The reasons and disasters of diffraction flows around H-type steel joints of diaphragm wall are analyzed. Combined with their main measures and shortcomings, a new kind of H-type steel joint for preventing diffraction flows is discussed on the. The rubber capsule is placed on the wall of H-type steel joint, and the grouting pipe is placed in the rubber capsule. Then the rubber capsule is expanded into the cement slurry and closely pastes on the side wall of the diaphragm wall, so as to prevent diffraction flows around the concrete channel. The proposed measures can be used in H-type steel joints and also in locked pipe ones.