Abstract: Waterborne polyurethane (WPU) dispersions and it's films with block structure were synthesized based on the step-growth addition polymerization of isophorone diisocyanate (IPDI) with poly (trimethylene carbonate) diols (PTMC-OH) of different molecular weights and their properties were investigated. The results revealed that the WPU dispersions with high solid content to 36%, and the viscosity and pH met the requirements of industrial products. Particle size of WPU dispersions is about 135 nm with narrow distribution. The obtained WPU dispersions could be directly applied to the field of water-based materials due to its excellent stability. On the other hand, the properties of WPU films were measured by SEM, FT-IR, GPC, DSC, TGA and other methods. The results indicated that the molecular weight of WPU films increased with increasing molecular weight of the PTMC-OH. Water droplet contact angle of WPU films is less than 90°, indicating that the films are hydrophilic. WPU film is a soft and tough polymer with elongation at break of 247.27%−941.53%. The initial decomposition temperature of WPU films is about 250−260 ℃. In summary, the synthesized WPU is a safe and environmentally friendly polymer with superior performance, which may be used in coatings, inks and adhesives to replace traditional solvent-based polyurethanes.