The study investigates whether the Book-tax differences and Abnormal Book-tax differences can detect firms that manipulate reporting earnings. We collect Book-tax differences data from companies’ financial reports by Chinese A-share firms listed on the Shanghai and Shenzhen Stock Exchanges from 2002 to 2010. The empirical results show that Book-Tax differences imply firms have the motivation of earnings management. Moreover, Book-tax differences has highly explanatory than Abnormal Book-tax differences in the earning management which firms avoid reporting earnings losses.