The 32m box girder model is an integrated rigid template assembled with segments, and the full set of model is composed of four parts including the bottom molds, side molds, end molds and the internal mold. The assembling quality is crucial to the appearance quality of the assembled model. This paper analyzes the quality problems during assembling of the 32 m box girder model and finds out the key factors affecting the assembling quality, and gives corresponding control methods, so as to improve the assembling quality of the model.