The utility model discloses a retaining wall soil pressure model experiment device under a plane strain condition. The problem that in the prior art, simulation of a test device does not conform to actual engineering is solved. The relation between the soil pressure and the lateral displacement in different displacement modes is determined; the retaining wall soil pressure model experiment deviceunder the plane strain condition has the beneficial effects that plane strain assumption in the complete sense is achieved, the model size is greatly reduced, and the experiment steps are simplified,and according to the scheme, the retaining wall soil pressure model experiment device under the plane strain condition comprises a U-shaped structure and a main wall body on one side, and a pluralityof pressure sensors are arranged on the surface of the main wall body; the side wall surrounds the U-shaped structure, and filler is arranged in the U-shaped structure; the propelling mechanisms are connected with the main body wall body, and the propelling mechanisms are arranged up and down, so that the upper half section and/or the lower half section of the main body wall body are/is driven bythe two propelling mechanisms to rotate or translate relative to the soil retaining base.