In this paper, we present a recent approach via variational methods and critical point theory to obtain the existence of solutions for the second order Hamiltonian system on time scale $\mathbb{T}$ $$\left\{\begin{array}{[email protected]{\quad}l}u^{\Delta^{2}}(t)+A(\sigma(t))u(\sigma(t))+\nabla F(\sigma(t),u(\sigma(t)))=0,& \hbox{\ $\Delta$-a.e. $t\in [0,T]_{_{\mathbb{T}}}^{\kappa}$,} \\u(0)-u(T)=0,\qquad u^{\Delta}(0)-u^{\Delta}(T)=0,& \hbox{}\end{array}\right.$$ where u Δ(t) denotes the delta (or Hilger) derivative of u at t, $u^{\Delta^{2}}(t)=(u^{\Delta})^{\Delta}(t)$ , � is the forward jump operator, T is a positive constant, A(t)=[d ij (t)] is a symmetric N�N matrix-valued function defined on $[0,T]_{\mathbb{T}}$ with $d_{ij}\in L^{\infty}([0,T]_{\mathbb{T}},\mathbb{R})$ for all i,j=1,2,�,N, and $F:[0,T]_{\mathbb{T}}\times \mathbb{R}^{N}\rightarrow\mathbb{R}$ . By establishing a proper variational setting, two existence results and two multiplicity results are obtained. Finally, three examples are presented to illustrate the feasibility and effectiveness of our results.