The invention provides a preparation method for a dual-curing resin monomer based on castor oil. The preparation method comprises the steps that castor oil fatty acid, a first catalyst and epoxy chloropropane are heated under stirring, react by controlling the temperature and then are cooled, calcium oxide and sodium hydroxide which have the equal mole number to the castor oil fatty acid are added, reacting is performed continuously, then reactants are filtered, sediment is removed, rotary evaporation is performed on obtained clear liquor to remove the epoxy chloropropane, and castor acid epoxy resin is prepared; the castor acid epoxy resin, a second catalyst and a polymerization inhibitor are weighed, simultaneously added into a reactor and heated under stirring by controlling the temperature, then unsaturated carboxylic acid is dropwise added, the temperature is increased, reacting is performed, finally reduced pressure distillation is performed to remove non-reacting substances, and then the dual-curing resin monomer based on the castor oil is prepared. The monomer can be cured through a mode of combining ultraviolet light curing with heat curing, the problem that the crosslinking degree is too low after the dual-curing resin monomer based on the castor oil is cured is solved, and therefore application of the castor oil among non-transparent materials, on substrates in complex shapes, in super-thick coatings and colored coatings and the like is facilitated.