中文摘要：

以我国12家主要券商研究机构的证券分析师推荐报告为样本，基于2000-2004年的沪深A股市场的全部股票价格与交易量数据库，采用三种不同的市场超额收益率模型和事件研究法，研究了我国证券分析师评级调整前后累积超额收益率、股票价格和交易量之间的经验关系，发现证券分析师增加到买人、增加到卖出、从买人中剔除评级调整对于投资者来说具有参考价值，但从卖出中剔除对于投资者不具备参考价值，证券分析师在作出从卖出中剔除评级调整时，对公司未来的盈利能力存在系统性乐观主义，研究结果为我国投资者正确使用证券分析师推荐报告提供了参考依据．

英文摘要：

Based on the database of China＇s A stock market between 2000 and 2004, this paper studies the empirical relationships among cumulative abnormal returns （CARs）, price and volume around analysts research reports recommendation revisions from twelve brokers by three abnormal cumulative market model and event study method. Results show that analysts＇ add-to-buy, add-to-sell, removed-from-buy recommendations are of investment value; the removed-from-sell recommendations are of no reference value. Analysts have systematic optimism about company＇s earnings. The results of this paper provide an important reference evidence for investors.