This invention relates to a composition for a preparation of polyurethane dispersion, comprising bio-based polyol as shown in structure (I) and polyhydroxy fatty acid compound as shown in structure (II): wherein, R represents a polyhydric alcohol unit that is selected from aliphatic polyhydric alcohol, alicyclic polyhydric alcohol, cyclic polyhydric alcohol, aromatic polyhydric alcohol, or optionally, cyclic polyhydroxyl having heteroatom; R\ represents a hydrocarbon unit obtained from a molecular chain of unsaturated fatty acid having 14-24 carbon atoms and having from 1-6 pairs of vicinal diol group per one molecular chain of such unsaturated fatty acid; n represents an integer from 2 to 8 of an ester group obtained from a reaction of polyhydric alcohol and unsaturated fatty acid; wherein said composition is prepared from a process comprising the steps of: i. mixing fatty acid comprising unsaturated fatty acid and polyhydric alcohol at a ratio of 1 mole equivalent or more of carboxylic group from unsaturated fatty acid per a hydroxy group from polyhydric alcohol; ii. adding organic acid and peroxide compound into the mixture from step i.; iii. adding nucleophilic substance into the mixture from step ii. under acidic condition.