The invention discloses a low-temperature resin composition and a preparation method thereof. The preparation method of the low-temperature resin composition comprises the steps of adding 15 parts by weight of low-molecular weight polyester resin, 30-50 parts by weight of phenolic novolac resin, 0-15 parts by weight of polyvinyl butyral resin and 100-240 parts by weight of solvent to a reactor, stirring for 1-2 hours at 40-60 DEG C, cooling to a room temperature, next, adding 40-60 parts by weight of epoxy resin and 1-5 parts by weight of hexamethylenetetramine, stirring thoroughly for dissolving, and finally, adding 0.5-5 parts by weight of nano silicon dioxide, and thoroughly dispersing and evenly stirring to obtain the low-temperature resin composition. The invention provides a low-temperature resin mixture which can be used as a support structure at minus 196 to 130 DEG C for a glass fiber cloth reinforcing material; the low-temperature resin mixture is especially applicable to low temperatures, has the characteristics of high strength, good toughness, not easy cracking and the like at low temperatures, and is excellent in product properties and high in practicability.