The commercial application of big data has been gradually under progress in various industries. The commercial application of big data in the hospitality industry, one of the significant elements in tourism industry, influences the thinking of hotel managers, at the same time, it concerns whether the hotel could remain an invincible position in the competition. The mining of the data on customers is conducive to the analysis of the behaviors and consuming preferences of customers, which can improve the living experience and satisfaction degree of customers effectively, in an effort to realize the profit of the hotel. J.W. Marriott and The Ritz-Carlton, representatives of the subordinate grand-level hotels in China of Marriott International, are selected as the research targets. This study adopts an empirical approach. We will have an in-depth interview with managers of the five main sections in each of the hotels, with the purpose of analyzing the tendency of the data use related to customers and its application level. In the light of the obtainment channel and actual application of big data of Marriott in China, it can judged that the hotel mainly applies the big data mainly to such aspects as sales of product, social media and online behavior of customers, offline data and shared data in multilateral platforms. In the end, on the basis of the case study, we can reach a conclusion that the commercial application of data in the hospitality industry will provide great assistance for hotel managers in formulating correct strategies of management and marketing.