The previous research paid little attention to the opportunity cost of the capital without considering lottery in cash rationing of Chinese IPOs. This paper focuses on the real initial return of the cash purchase and analyzes its rationality and influencing factors. We test the related issues using a sample of A-share IPOs in cash rationing during year 1998~2007. The results indicate that (1) the investors in the primary market may not get the high abnormal initial return from IPO purchase; (2) the noise purchase in the primary market can reduce the return; (3) the noise trading in the secondary market can improve the return; (4) a higher offering price-earning ratio or a larger size of the company can improve the return by limiting the noise purchase.