Homogenization for non-local operators in periodic environments has been studied intensively. So far, these works are mainly devoted to the qualitative results, that is, to determine explicitly the operators in the limit. To the best of authors' knowledge, there is no result concerning the convergence rates of the homogenization for stable-like operators in periodic environments. In this paper, we establish a quantitative homogenization result for symmetric $α$-stable-like operators on $\R^d$ with periodic coefficients. In particular, we show that the convergence rate for the solutions of associated Dirichlet problems on a bounded domain $D$ is of order $$ \varepsilon^{(2-α)/2}\I_{\{α\in (1,2)\}}+\varepsilon^{α/2}\I_{\{α\in (0,1)\}}+\varepsilon^{1/2}|\log \e|^2\I_{\{α=1\}}, $$ while, when the solution to the equation in the limit is in $C^2_c(D)$, the convergence rate becomes $$ \varepsilon^{2-α}\I_{\{α\in (1,2)\}}+\varepsilon^α\I_{\{α\in (0,1)\}}+\varepsilon |\log \e|^2\I_{\{α=1\}}. $$ This indicates that the boundary decay behaviors of the solution to the equation in the limit affects the convergence rate in the homogenization.