The invention belongs to the technical field of epoxy resin materials, and in particular relates to an epoxy resin curing agent, a method for preparing the same and application thereof. The preparation method is characterized by: adding water into ethanol solution of organic alkoxy silane monomers, and preparing oligosiloxane through hydrolytic condensation; performing chemical grafting reaction on the oligosiloxane and alkylphenol (the carbon number n of the alkyl group is 1 to 30), and adding polybasic amine for chemical reaction or physical mixing to prepare the novel epoxy resin curing agent. In the method, the curing agent is prepared by adding the alkylphenol and the oligosiloxane, the synthetic process is simple, the reaction conditions are mild, the compatibility between the curing agent and the epoxy resin is good, and the impact resistance, the weathering resistance, the strong acid-alkali resistance, the salt-fog resistance and the like of the epoxy system are improved. Thecuring agent can be applied in various fields of heavy corrosion resistant coatings, epoxy coatings, epoxy adhesives, epoxy composite materials, epoxy electrical packaging materials and the like.