“…Therefore, it is of practical importance and mathematical significance to consider the existence of homoclinic solutions of Hamiltonian systems emanating from the origin. The existence and multiplicity of homoclinic orbits for the first order system were studied extensively by means of critical point theory, and many results were obtained under the assumption that H(t, z) depends periodically on t (see [4,10,13,16,22,33,45,46,48,49,50,51,52,56] and the references therein). As authors known, the periodicity is used to protect some kind of compactness such as the (PS) condition.…”