We　investigate　the　quantum　phase　transition　(QPT)　and　quench　dynamics　in　the　anisotropic　Rabi　model　when　the　ratio　of　the　qubit　transition　frequency　to　the　oscillator　frequency　approaches　infinity.　Based　on　the　Schrieffer-Wolff　transformation,　we　find　an　anti-Hermitian　operator　that　maps　the　original　Hamiltonian　into　a　one-dimensional　oscillator　Hamiltonian　within　the　spin-down　subspace.　We　analytically　derive　the　eigenenergy　and　eigenstate　of　the　normal　and　superradiant　phases　and　demonstrate　that　the　system　undergoes　a　second-order　quantum　phase　transition　at　a　critical　border.　The　critical　border　is　a　straight　line　in　a　two-dimensional　parameter　space　which　essentially　extends　the　dimensionality　of　QPT　in　the　Rabi　model.　By　combining　the　Kibble-Zurek　mechanism　and　the　adiabatic　dynamics　method,　we　find　that　the　residual　energy　vanishes　as　the　quench　time　tends　to　zero,　which　is　a　sharp　contrast　to　the　universal　scaling　where　the　residual　energy　diverges　in　the　same　limit.