A variant of a Gaussian approximation in Ising model of phase transition is suggested.The method of functional integration with the application of a variational method is put in the basis of the approach.The Hamiltonian (the functional) is presented which in the method of functional integration produces the known results of a two-tails approximation obtained by a diagram method.The application of a variational method eliminates a principal demerit of the two-tails approximation -incorrect description of the phase transition order.The results of numerical calculations for two and threedimensional lattices are presented.