A series of waterborne polyurethane emulsions containing long-chain alkyl groups in side chains were prepared using polyneopentyl adipate (PNA), dimer acid polyester polyol (BY3026) and isophorone diisocyanate (IPDI) as the main raw materials. The structure of the film was characterized by infrared test, and the properties of the emulsion and films were analyzed by tests such as particle size, mechanical stretching, water absorption, contact angle and adhesion on biaxially oriented polypropylene film (BOPP). The results show that when the mass ratio of BY3026 to PNA increases from 0% to 60%, the particle size of the emulsion increases, the water resistance of the film increases, and the surface energy first decreases and then increases, the tensile strength and elongation at break decreased from 52.6 MPa and 2607.2% to 38.7 MPa and 1911.2% respectively. When m(BY3026):m(PNA)=2:5, polyurethane has the best compatibility with BOPP film, the surface energy is 35.41 mJ/m2, and the T-peel strength on BOPP film is 2.98 N/25 mm.