The invention provides a high-chloride-capacity liquid-phase dechlorinating agent as well as a preparation method and an application thereof. The high-chlorine-capacity liquid-phase dechlorinating agent is suitable for removing inorganic chlorine from an oil product and is particularly suitable for removing hydrogen chloride from reformate. A carrier of the dechlorinating agent is a carbon molecular sieve, active ingredients of the dechlorinating agent comprise an alkali metal and an alkali earth metal oxide, and an auxiliary agent component is copper oxide, ferric oxide or zinc oxide. The preparation method of the solid dechlorinating agent provided by the invention comprises the following steps: dipping soluble copper salt, calcium salt, magnesium salt, barium salt and the like to a cylindrical carbon molecular sieve, drying, and performing stabilizing treatment to obtain the dechlorinating agent. The dechlorinating agent provided by the invention has the advantages of being relatively high in chloride capacity, low-price and easily available in raw material, having active ingredients uniformly distributed on the carrier, good in thermal stability, strong in water resistance, high in mechanical strength and the like, and the dechlorinating agent has desulfurization and denitrification effects at the same time.