  Based on the renormalisability of the SU(n) theory with massive gauge bosons,
we start with the path integral of the generating functional for the
renormalized Green functions and develop a method to construct the scattering
matrix so that the unitarity is evident. By using as basical variables the
renormalized field functions and defining the unperturbed Hamiltonian operator
$H_0$ that, under the Lorentz condition, describes the free particles of the
initial and final states in scattering processes, we form an operator
description with which the renormalized Green functions can be expressed as the
vacuum expectations of the time ordered products of the Heisenberg operators of
the renormalized field functions, that satisfy the usual equal time commutation
or anticommutation rules. From such an operator description we find a total
Hamiltonian $\widetilde{H}$ that determine the time evolution of the Heisenberg
operators of the renormalized field functions. The scattering matrix is nothing
but the matrix of the operator $U(\infty, -\infty)$, which describes the time
evolution from $-\infty$ to $\infty$ in the interaction picture specified by
$\widetilde{H}$ and $H_0$, respect to a base formed by the physical eigen
states of $H_0$. We also explain the asymptotic field viewpoint of constructing
the scattering matrix within our operator description. Moreover, we find a
formular to express the scattering matrix elements in terms of the truncated
renormalized Green functions.
