The invention discloses an anti-aging sealant and a preparation method thereof. The sealant comprises the following components in parts by weight: 20-30 parts of coumarone indene resin, 5-10 parts of polysulfide rubber, 5-10 parts of nitrile-butadiene rubber, 8-15 parts of tert-butyl phenol-formaldehyde resin, 3-7 parts of silicon dioxide, 2-6 parts of chlorosulfonated polyethylene, 2-7 parts of butyl acrylate, 1-5 parts of aluminum powder, 3-7 parts of sodium metasilicate, 2-8 parts of phosphate, 1-4 parts of triethanolamine, 1-5 parts of boron nitride, 0.5-2 parts of paraffin, 1-3 parts of 2,4-dihydroxy benzophenone and 0.8-3 parts of butyl p-hydroxy benzoate. The preparation method comprises the following steps: adding the components into a reaction kettle, uniformly mixing, heating to 120-140 DEG C under vacuum conditions, stirring to react for 120-180 minutes, and cooling to room temperature. The sealant disclosed by the invention has the advantages of favorable aging resistance and excellent adhesive property, and is more suitable for the field of solar energy.