We consider a dual channel supply chain in which a manufacturer sells a single product to end-users through a traditional retail channel and a manufacturer-owned direct online channel. This paper analyzes the profits and the demands of the manufacturer and retailer in three service policies of the retailer using Stackelberg game. Combined with the numerical example, the results show that: The profits and demands of both sides increase in all the policies with the spillover effect of price on demand increase; The retailer will profit most and get largest market demand from providing ex post service, which means that the retailer may voluntarily becomes the Stackelberg follower for higher profit; Providing ex ante service doesn't benefit the retailer a lot.