  In this paper, we are concerned with the existence and asymptotic behavior of
least energy solutions for following nonlinear Choquard equation driven by
fractional Laplacian $$(-\Delta)^{s} u+\lambda V(x)u=(I_{\alpha}\ast F(u))f(u)
\ \ in \ \ R^{N},$$ where $N> 2s$, $ (N-4s)^{+}<\alpha< N$, $\lambda$ is a
positive parameter and the nonnegative potential function $V(x)$ is continuous.
By variational methods, we prove the existence of least energy solution which
localize near the potential well $int (V^{-1}(0))$ as $\lambda$ large enough.
