In order to solve the problem of low mechanical properties of waterborne bio-based polyurethane，a waterborne UV-curable bio-based polyurethane was synthesized using bio-based polyols（castor oil and isosorbide）， isophorone diisocyanate，2，2-hydroxymethylpropionic acid，pentaerythritol triacrylate and trimethylamine. The structures of emulsion were characterized by Fourier transform infrared spectroscopy（FT-IR），nuclear magnetic resonance spectroscopy，zeta potential instrument and nanoparticle size analyzer. The mechanical properties，transmittance and other basic properties of coating were also studied. The results showed that，with the increase of isosorbide content，the tensile stress increased from 4. 9 MPa to 26. 8 MPa，the elongation at break decreased from 269% to 4. 1%，and the light transmittance of each coating remained above 90% in the visible light. Therefore，the mechanical properties of bio-based polyurethane coating were significantly improved with a suitable ratio of castor oiland isosorbide，and good transparency in the visible light was also abtained.