The reinforcement width and depth of trench face soil body of diaphragm wall should satisfy not only the requirement of stability of trench face but also the requirement of anti-sliding (anti-shearing)

anti-capsizing and anti-bending capability of reinforcement body. The paper first analyzes the relationship between the lots of influencing factors and the stability safety factors of trench face

and it also sums up the key influencing factors and the important controlling parameters which are the reinforcement width and depth. Then it puts forward the checking principle and the safety criteria for the anti-sliding (anti-shearing)

anti-capsizing and anti-bending capability

and also presents the calculation methods of width and depth (length) of mixing pile reinforcement body. In addition it puts forward measures which can upgrade the stability of trench face by means of inserting steel material into mixing pile top and embedding steel material in guide wall and arranging mixing piles into outer arch in the plane. The verification of calculation methods of mixing pile reinforcement width and depth is carried out

and the calculus of being upgraded stability safety factors of trench face by means of inserting steel material into mixing pile top and embedding steel material in guide wall and arranging mixing piles into outer arch in the plane is also given. Finally

it provides the research prospect on this topic.