The study is to find the relationship between brand concept consistency and the consumer attitude toward the extended brand and the moderating roles of knowledge, involvement and typicality on their relationships in the food-service industry. In the severely competitive market, brand extension strategy has become a key strategy to the companies that are trying to expand in the new market and to cut down the marketing cost. First , the similarity which is measured by consistency of brand concept has a positive effect on the consumer attitude toward the extended brand. Second, the knowledge on the original brand has moderating effect on the relationship between consistency of brand concept and the consumer attitude toward the extended brand. More knowledge brings on more favorable attitudes.