Abstract: Taking broker as the research object, we get 63388 investment rating samples for 1597 domestic A shares made by 2805 analysts employed by 111 brokers in order to test the affection of broker’ interests and information advantage on the information contents and the optimism degree of analysts’ rating and market reaction. The results show that analysts’ rating for brokers’ self-trading stocks and institution investors’ heavy-holding stocks have less information contents and are more optimistic due to the conflicts of interests; underwriting relationship can’t add information contents; reputation has more pressure on individual analysts while less on brokers; star analysts provide superior recommendations; geography adjacent to headquarter location adds information contents; the market does react to investment rating. All these conclusions can be used to screen investment ratings, thus helping to protect the interests of investors.

Key words: investment rating, information contents, Brokers&rsquo, Conflicts of broker interests, information advantage