This study investigates the effect of income smoothing on financial statement comparability. The proxy of financial statement comparability is calculated according to De Franco et al. (2011)’s method. The proxy of income smoothing is calculated according to Tucker and Zarowin (2006)’s method and modified Jones model(Dechow et al. 1995). The results are as follows. First, we find that the comparability increases when the level of income smoothing is higher. Second, we find that the group that is likely to smooth income by using discretionary accruals is positively related to the comparability. Additionally, we find that the comparability increases when the level of the interaction between earnings management and income smoothing is higher. Second, we use the change variables to control the effect of endogeneity of earnings management and income smoothing on financial statement comparability, and we find that the negative relationship between earnings management and the comparability and the positive relationship between income smoothing and the comparability, which makes our results robust. The difference of the study compared to previous research is as follows. De Franco et al. (2011) make a new comparability measure in terms of a function connecting economic events and financial statements. They find that financial statement comparability is positively related to analyst following and forecast accuracy. Sohn(2016) investigates the relationship between earnings management and comparability, and finds that accrual-based earnings management decreases and real earnings management increases when accounting system comparability is high. We divide earnings management into opportunistic earnings management with high volatility and income smoothing with low volatility. We find that opportunistic earnings management with high volatility decreases financial statement comparability, but income smoothing with low volatility increases financial statement comparability. The results of this study confirm that high volatile opportunistic earnings management and income smoothing have different effects on financial statement comparability and we extend Sohn(2016)’s study.