Motivated by a result of Treibergs, given a smooth function f(y) on the standard sphere S^2, and any positive constant H_0, we construct a spacelike surface with constant mean curvature H_0 in the Schwarzschild spacetime, which is the graph of a function u(y, r) defined on r>r_0 for some r_0>0 in the standard coordinates exterior to the blackhole. Moreover, u has the following asymptotic behavior: |u(y,r)-r_*-(f(y)+r^{-1}\phi(y)+1/2 r^{-2}\psi(y)|\le Cr^{-3} for some C>0, where r_*=r+2m\log(r/(2m)-1). Here \phi, \psi are functions determined by f and H_0. In particular, the surface intersects the future null infinity with the cut given by the function f. In addition, we prove that the function u-r_* is uniformly Lipschitz near the future null infinity.