  Two kinds of Yang-Mills fields are found upon the concepts of mass eigenstate
and nonmass eigenstate. The Yang-Mills fields of the first kind were proposed
by Yang and Mills, which couple to the mass eigenstates with the same rest
mass, whose gauge bosons are massless. I find that there are second kind of
Yang-Mills fields, which are constructed on a five-dimensional manifold. Only
the nonmass eigenstates couple to the Yang-Mills fields of the second kind,
which are the nonmass eigenstates as well and composed of mass eigenstates of
gauge bosons. The mass eigenstates of the Yang-Mills fields of the second kind
live in the four-dimensional spacetime, the corresponding gauge bosons of which
may be massive. The SU(2)\times U(1) gauge fields of the second kind are
studied carefully, whose gauge bosons, which are the mass eigenstates, are the
W^{\pm}, Z^{0} and photon fields. The rest masses of W^{\pm} and Z^{0} obtained
are the same as that given by the Glashow-Salam-Weinberg model of electroweak
interactions. It is discussed that this model should be renormalizable.
