Many studies investigate the traditional bullwhip effect from the viewpoint of the upstream inventory plan． However，this paper studies the inventory bullwhip effect from the supply chain downstream perspective and derives new managerial implications． More practical factors，such as market scale，price sensitivity coeffi-cient，etc． are modeled into the demand function． A simple supply chain including one retailer and one manu-facturer is constructed，who adopts the order-up-to policy and MMSE technique． There are two types of infor-mation sharing between the retailer and the manufacturer． The expressions of inventory bullwhip effects of the manufacturer with different types of information sharing are given，and the factors influencing bullwhip effects are analyzed． A numerical analysis is applied to test our model and some new findings are derived． The results indicate that: 1) information sharing can significantly reduce the manufacturer’s bullwhip effect of inventory， 2) neither the retailer’s bullwhip effect of inventory nor the manufacturer’s is influenced by the market scale， 3) the retailer’s bullwhip effect of inventory will not exist under some special conditions，4) compared with the retailer’s lead time，the manufacturer’s lead time affects the manufacturer’s bullwhip effect of inventory more dramatically，5) the price sensitivity coefficient and price correlation coefficient also have impacts on the bullwhip effect．