For a nearly integrable Hamiltonian systems H = h(p) + ǫP (p, q) with (p, q) ∈ R 3 × T 3 , large normally hyperbolic invariant cylinders exist along the whole resonant path, except for the √ ǫ 1+d -neighborhood of finitely many double resonant points. It allows one to construct diffusion orbits to cross double resonance.[Z2] Zhou M., Infinity of minimal homoclinic orbits, Nonlinearity 24 (2011) 931-939.