The utility model relates to a horizontal tunnel model test device in cavity behind simulation lining wall, the device be side -mounting center piece in tunnel lining, fillet behind tunnel lining outside installation wall, the fillet adopts the piecemeal pin -connected panel behind its mesospore, and prelude, afterbody and the top of each piecemeal are equipped with tenon, tongue -and -groove, protruding point respectively to each piecemeal is conveniently fixed a position, is installed and removed, through removing center piece with simulation tunnel excavation, remove behind the wall cavity after with the simulation wall of a plurality of piecemeals in the fillet through the part. The utility model discloses an installation with remove center piece, realized the process of the test of excavation behind the first loading, more accord with mountain tunnel's engineering characteristics, through the installation with remove a plurality of piecemeals in the fillet behind the wall, can go on portably simulating effectively to cavity behind the wall of different how much characteristics (like different positions, equidimension not), especially in duplicate test, avoided building again country rock and local loaded down with trivial details work of excavating the country rock.