The invention belongs to the technical field of forest product chemical product manufacturing, and specifically relates to a rosin modified phenolic resin for a vacuum paint spraying high-grade coating and a preparation method of the rosin modified phenolic resin. The preparation method of the rosin modified phenolic resin for the vacuum paint spraying high-grade coating, provided by the invention, comprises the following steps: firstly reacting tert-octylphenol with formaldehyde in different proportions under sodium hydroxide to prepare phenolic resin with different dissolubility, carrying out esterification on rosin through pentaerythritol to obtain rosin resin, carrying out a synthetic reaction on phenolic resin and the rosin resin in different proportions, then adding an antioxidant and an anti-ultravoilet assistant, and then carrying out refining to obtain the rosin modified phenolic resin. According to the method, the rosin modified phenolic resin for the vacuum paint spraying high-grade coating is prepared by adopting a numerical control method, the condition is easy to control, the rosin modified phenolic resin with different softening points and different dissolubility canbe produced, the prepared rosin modified phenolic resin is excellent in performance, high in softening point, low in color and luster, small in acid value and high in viscosity, and has extremely high dissolubility and molecular weight, and the product quality is easy to control.