A series of humic acid modified waterborne polyurethane emulsions (HAWPU) were successfully synthesized with poly-caprolactonediol (PCL), isophoronediisocyanate (IPDI), dimethylolpropionic acid (DMPA), trimethylolpropane (TMP) as the basic raw material and humic acid (HA) as the modifier. The structural characterization and performance tests of HAWPU were carried out by FTIR, DLS, TGA, SEM and mechanical analysis. The effects of HA addition on the appearance, particle size and Water absorption rate, thermal stability and mechanical properties of HAWPU emulsion were investigated. The results showed that HAWPU emulsions had good particle size distribution and storage stability. When the HA mass fraction is 0.3% (accounting for the total mass of the emulsion system), the average particle size of the HAWPU emulsion is only 47.60 nm. The tensile strength of the film can reach 52.54MPa, which is 55.8% higher than WPU. The thermal stability is also significantly improved, and the temperature at which the mass fraction is lost by 50% (the mass before the film is pyrolyzed) is 334 ℃, which is higher than that of the WPU film (322 ℃).