Using the method of moving planes, we establish the radial symmetry of positive solutions to the fractional systemin the entire Euclidean space R n and in the unit ball, where 0 < s, t < 1 and p, q ≥ 2. In particular, our result can be applied to the nonlinearities f (u, v) ≡ u a v b and g(u, v) ≡ u c v d , where a, d ∈ R and b, c > 0.