This paper researches on the influence of accounting conservatism and asymmetric information on SEO announcement effect by accrual measurement method and respectively measuring accounting conservatism and asymmetric information by the internal rate of return volatility. The results show that accounting conservatism and the SEOCAR has significant positive correlation on cumulative abnormal return at 5% level，i.e. the higher the accounting conservatism level is, the less the negative effect is. Meanwhile the paper finds significant negative correlation between information asymmetry and SEOCAR at 10% level, but the accounting conservatism can't play a role in weakening asymmetric information. 