Abstract: Demand information sharing plays an important role to reduce total inventory cost in the system of one warehouse with multiple retailers. Under the preconditions that the periodic check-up is taken as inventory strategy at all nodes in the system, replenishment is to be done at fixed intervals, lead time is comparatively shorter than replenishment interval and emergency replenishment from upstream supplier(s) is available when stock-out happens, the ETC (expected total cost) models are developed in either case, i.e., information' shareable in collaborative commerce or unavailable to get. A numerical example is given to illustrate that the demand information sharing can attain the goal to reduce the cost of the system and that keeping the highest inventory level dynamical is indispensable to the benefit which the central warehouse is attempting through demand information sharing.