Research conclusions;(1)For twin-cell box girders，there are more shear lag effect models corresponding to its longitudinal symmetric load model，meanwhile there is much difference between different models.(2)In all shear lag effect models，the most prominent model is concentrated force only applied on mid web. Also，this model is affected by the height-span ratio most obviously.(3)Considering the multiple patterns of shear lag effect，in designing of mufti- cell box girder, the influence of different load models of shear lag effect should be considered fully. ( 4 ) The simulation method and results of this paper have some reference value for design and mechanical analysis of mufti-cell box Girders.