Nowadays enterprises use brand strategy to enhance product¡¦s depth and width, raising the customers¡¦ evaluation on brand. To lower the cost of launching a new product, enterprise usually uses line extension to launch a new product. Most researches about the effect of product line extension on consumer evaluation all focus on physical product. Research focuses on service product is rare. This study focuses on service product, and wants to know the application of vertical extension strategy in service industry. Although extension direction is main strategy when doing product line extension in practical use, extension direction is considered as moderating variable to others, not main issue in previous academic studies. Thus this study treats extension direction as main body of the research, and discusses the changes of consumers¡¦ attitudes towards parent brand and extension brand in different situation. This study chooses two hotels, The LALU and CHINATRUST Hotel which are real and have different brand concepts, as the design scenario, using experiment design to understand consumers¡¦ evaluations at extension service and parent brand when facing different directions of product line extension. Besides, this study uses service continuity to replace ownership effect, and chooses extension direction as main effect, observing the interaction between extension direction and brand concepts, service continuity and branding strategy, trying to understand the factors influencing consumers¡¦ evaluation in product line extension. This study finds consumers¡¦ evaluation of upward extension is significantly higher than downward extension during product line extension. However, no matter upward or downward, consumers¡¦ evaluation on parent brand become lower. The prestige-oriented brand concept enhances this negative effect, but branding strategy of subbrand can ease this effect.