In this paper we proposed a case-based reasoning (CBR) mechanism with improved vector space model. In order to get more accuracy of case retrieval, this paper presents the improved algorithm of the text feature-weight calculation and Chinese word order calculation. And a supermarket guiding robot is designed to verify the reasoning machine as an example. The experiments show that compared with the traditional CBR reasoning machine which uses the nearest neighbor algorithm, the improved CBR reasoning machine can get more accurate and reasonable result, and better meet the demands of customers.