The HDI trimer (HT) modified aqueous polyurethane dispersions(HPUD) were synthesized and the effects of the contents of HT on the water- and solvent-resistance, the degree of crosslinking, hardness, gloss and surface drying time of the HPUD films were discussed. The particle sizes and its distributions, structures and thermal stability of HPUDs and its film were characterized by dynamic light-scattering technique (DLS), infrared spectra (IR) and thermal gravimetric analysis (TGA), respectively. The results show that introducing 5–10 wt% of HT into PUD improve surface dry rate and crosslinking degree of HPUD films, the HPUD films with 10% HT possess better performance including 45 min of the surface drying time, 80% of the crosslinking degree, 78% and 7% of the alcohol- and water-absorption rate. On the other hand, HPUDs display faster film hardness increasing rates and slightly lower final films hardness than those of the common PUDs without HT modification. DLS analysis results show that the particle sizes and its distributions increase and storage stability decrease with increasing the HT content in the HPUD up to 20% during the storage process. TGA curves indicate that the HPUD films possess good thermal stability.