The invention discloses a slide-type large-scale underground test platform model test filling apparatus and a method thereof, which belong to the field of model test filling. The apparatus comprises aplatform balance, a trolley, a rest platform, a slide apparatus, a vertical steel plate, a hinge, a bolt, a vertical baffle plate, a model case, a vertical support bar, a steel plate groove, and an anti-impact sleeve. The slide apparatus is composed of a funnel form slide, a head slide, a central slide, a tail slide, and a replaceable curvature outlet. a main part of the funnel-form slide and thevertical steel plate are connected by the movable hinge, and the vertical steel plate can be freely rotated. The vertical baffle plate is supported at a case wall of one side of the model case, and the vertical baffle plate has effect for preventing downslide of the slide apparatus. The slide-type large-scale underground test platform model test filling apparatus can be rapidly assembled, after test filling is completed, dismounting is simple, the filling speed is fast, and labour saving and time saving can be realized. According to a practical space position relation of a test platform and the top of the model case, the linear-type slide or a curve-type slide is subjected to segment erection, and large flexibility can be provided.