In this paper, we study the following critical system with fractional Laplacian:where (-) s is the fractional Laplacian, 0 < sis a fractional critical Sobolev exponent, N > 2s, 1 < α, β < 2, α + β = 2 * , is an open bounded set of R N with Lipschitz boundary and λ 1 , λ 2 > -λ 1,s ( ), λ 1,s ( ) is the first eigenvalue of the non-local operator (-) s with homogeneous Dirichlet boundary datum. By using the Nehari manifold, we prove the existence of a positive ground state solution of the system for all γ > 0. Via a perturbation argument and using the topological degree and a pseudo-gradient vector field, we show that this system has a positive higher energy solution. Then the asymptotic behaviors of the positive ground state solutions are analyzed when γ → 0.