We propose a grand unified theory (GUT) in which the gauge symmetry is dynamically broken by a strongly coupled gauge interaction, analogous to the chiral symmetry breaking in QCD or technicolor theory. GUT is a beautiful idea and surprisingly consistent with supersymmetry (SUSY). As well as the fact that all the fermions fit to a representation in GUT groups, the three gauge coupling constants meet at a very high energy scale with the particle content of the minimal SUSY standard model. However, the realistic model building of GUT has various difficulties such as the doublet-triplet Higgs mass splitting problem and the too rapid proton decay. Also, since the GUT appears to be a theory at very high energy scale, it is the usual case that there is no definite prediction to the low energy physics. We propose a realistic model without above problems by using the dynamical GUT symmetry breaking. The model provides an interesting predictions to the gaugino mass relation in low energy which should be easily testable with the LHC and a linear collider.
