Using the sample listed companies of SEM and GEM board in China from 2009 to 2015, the paper examines the effect of internal control on the quality of earnings preannouncement. The study shows that sound internal control reduces the probability of the material misstatement of earnings preannouncement and errors of earnings preannouncement. However, the effect of internal control on earnings preannouncement is more significant for non SOE listed companies. Furthermore, if the companies have no material internal control weakness, the possibility of material misstatement and errors in earnings preannouncement will be lower. In addition, the higher the quality of internal control information disclosure, the higher the quality of earnings preannouncement. The results show that sound internal control can improve the quality of earnings preannouncement. The conclusion of this paper supports the opinion that internal control can improve the quality of accounting information from the perspective of earnings preannouncement.