  The possibility of dynamical electroweak symmetry breaking by strong coupling
gauge interaction in models with D-branes in String Theory is examined. Instead
of elementary scalar Higgs doublet fields, the gauge symmetry with strong
coupling (technicolor) is introduced. As the first step of this direction, a
toy model, which is not fully realistic, is concretely analyzed in some detail.
The model consists of D-branes and anti-D-branes at orbifold singularities in
(T^2 x T^2 x T^2)/Z_3 which preserves supersymmetry. Supersymmetry is broken
through the brane supersymmetry breaking. It is pointed out that the problem of
large S parameter in dynamical electroweak symmetry breaking scenario may be
solved by natural existence of kinetic term mixings between hypercharge U(1)
gauge boson and massive anomalous U(1) gauge bosons. The problems to be solved
toward constructing more realistic models are clarified in the analysis.
