The invention discloses rosin polyisocyanate for rigid polyurethane foam, which has a structural formula shown in the specifications. The rosin polyisocyanate for the rigid polyurethane foam is prepared by the reactions shown in the specifications, wherein a sulfonyl chlorination reagent used in sulfonyl chlorination is thionyl chloride and the reaction is performed at room temperature. The rosinpolyisocyanate is prepared without the conventional phosgene method and the reaction conditions are mild; isocyanate is prepared from renewable rosin serving as a raw material; and when the rosin is used in the preparation of the rigid polyurethane foam, the dependence of the polyurethane industry on a petroleum raw material is reduced and sustainable development is facilitated.