By using the companies in the manufacturing sector listed in the Shanghai Stock Exchange and Shenzhen Stock Exchange during 2007—2012 as the research object, we do an empirical research on how customer concentration affects a companys financial results, operating risks and market performance. The results show that customer concentration has a significantly negative impact on gross profit margin (GPM) and degree of operating leverage (DOL), and has a significantly positive correlation with price to sales (PS). The research findings provide a new empirical evidence for the relationship among business, finance and market. The rising of customer concentration leads to the simultaneous falling of financial results and operating risks, the capital market positively responses to the rising of customer concentration, and the customer concentration and its change can be viewed as a kind of signal for investment decision.