In the present article, by using coupling technique, we establish the relation between Ising model and contact process. From this relation, the upper limit of critical temperature of higher dimensional Ising model is obtained. That is, the critical point βc(n) of n-dimensional Ising model must satisfy exp2βc(n)(2n-1)·(exp2βc(n)-1)≥2/2n-1 and especially, crirical point βc(3) of the three-dimensional Ising model must satisfy βc(3)> 1/2ln1.17.