The invention discloses a preparation method of two cardanol-base polyalcohols and polyurethanes thereof, which comprises the following steps: (1) directly carrying out sulfhydryl-alkene addition reaction on cardanol side chain unsaturated double bond and sulfhydryl monoalcohol under the irradiation of ultraviolet light to prepare the side chain cardanol-base polyalcohol with controllable hydroxyl number; (2) reacting hendecene acyl chloride and phenolic hydroxyl group of cardanol to prepare 10-undecylenic acid modified cardanol, reacting with sulfhydryl monoalcohol to prepare 10-undecylenic acid modified cardanol-base polyalcohol with controllable hydroxyl number; and (3) reacting the cardanol-base polyalcohol and 10-undecylenic acid modified cardanol-base polyalcohol with diisocyanate to prepare the cardanol-base polyurethanes. The method has the advantages of low cost, no environmental pollution and the like, and is renewable and biodegradable; and the generated polyurethane resin can be used as a resin for paints and adhesives.