In order to study the optimal division method of the box chamber for steel-concrete composite wide-deck bridge, respectively from the perspective of longitudinal stress of the bridge, transverse stress of bridge deck and related engineering measures, the control variable method is used to calculate and analyze the case of composite beam according to according to the current bridge design specifications. The economical and reasonable method of dividing the box chamber of the composite beam wide-deck bridge is given, and the suggested parameter values are obtained.