In current market competition companies face with short product life cycle, high demand uncertainty and drastic declines of product values. This study analyses the price protection policy in channel coordination and proposes a two-period dynamic model of optimal price protection rate based on the single ordering. The result shows that, through setting reasonable the wholesale price and the price protection rate, optimal order quantity by the retailer can be achieved. Furthermore, The policy optimizes the total benefit of channel alliance to obtain the win-win pattern, and finally realize channel coordination.