In order to study the application effect of air-lift reverse circulation in slag removal of diaphragm wall groove bottom, Fluent software was used to establish a two-dimensional model by means of simulated numerical analysis method. The placement depth of air-lift mixer, slag cleaning pressure of air compressor and slag diameter are taken as the research objects. It is concluded that the air-lift reverse circulation technology can effectively remove slag from the foundation pit bottom of diaphragm wall. The velocity of slag flowing out is 0.014～1.098m/s, the escape velocity of clay particles is faster than that of slag with other sizes; and the thicker the slag is, the more difficult the slag removal is.