We study the existence of even homoclinic orbits for the second-order Hamiltonian systemü+V u (t, u) = 0. Let V(t, u) = −K(t, u)+W(t, u) ∈ C 1 (R×R n , R), where K is less quadratic and W is super quadratic in u at infinity. Since the system we considered is neither autonomous nor periodic, the (PS) condition is difficult to check when we use the Mountain Pass theorem. Therefore, we approximate the homoclinic orbits by virtue of the solutions of a sequence of nil-boundary-value problems.