[en] Combining a unitary transformation, the variational method and the exact ground state of pure gauge Hamiltonian, the vacuum structure and spontaneous chiral-symmetry breaking are systematically investigated in (1+1)- and (2+1)-dimensional Hamiltonian lattice gauge theories with fermions, and nice scaling behaviors for <ψ-barψ> extending to the weak coupling regime is obtained. This paper not only reproduces well the exact value in the continuum Schwinger model, but also predicts the values for the fermion condensates in QCD₂, QED₃ and QCD₃