Precision in earning report has always been a concern among investors, and when there are some negative adjustments on earning, investor may find it challenging to decide whether they should hold or sell their shares. This paper studies the impact of earning precision and unexpected earning adjustments on firms whose share are listed on Tehran Stock Exchange. The proposed study of this paper considers three hypotheses including whether earning precision has negative relationship with unexpected profit, whether it has a negative with unexpected decline in profit and finally, whether, in prediction on negative news compared with positive news, there is a negative relationship between stronger earnings forecast and precision of earning forecast. The study gathers the necessary data from official news released for some firms whose shares were active over the period 2003-2012. The study uses two regression models and the results of regression analysis have confirmed all hypotheses of this survey.