The invention relates to a dehalogenation and degradation method for a halogenated aromatic compound. The method includes the steps that the halogenated aromatic compound is used as raw materials, alcohol is used as a hydrogen source, and water is used as a solvent; under the action of a supported catalyst, a reaction is performed for 5-50 h at the temperature being 30-260 DEG C under the pressure ranging from 1 MPa to 10 MPa, and the halogenated aromatic compound is subjected to water-phase hydrogen production in-situ dehalogenation and degradation, wherein a benzene ring of the halogenated aromatic compound at least contains one F or Cl or Br or I substituent group, the supported catalyst is formed by active components and a carrier, the active components are composed of mixtures of transitional metal and other metal, the transitional metal is one of Rh, Pd, Pt and Ni, the other metal includes one of Se, Ca, Ba, La and Ce, and the carrier is one of active carbon, kieselguhr, zeolite, gamma-Al2O3, AlF3 and MgO. Active hydrogen is prepared to directly participate in the reaction through in-situ catalysis instead of directly using H2 as a reducing agent. Thus, the dehalogenation and degradation method has the beneficial effects of being high in reaction activity, selectivity and security, environment-friendly and the like, and having the good application prospect.