Vinyl polymer (dimethyl diallyl ammonium chloride /acrylic acid/2-hydroxyethyl acrylate/acrylamide) was synthesized via free radical polymerization, and then vinyl polymer/zinc oxide nano composite (PDM/ ZnO) was prepared by ultrasonic treatment and used for leather tanning agent. PDM and PDM/ZnO was characterized by FT-IR and XRD. The morphology of nano composite was observed by TEM. Moreover, PDM and PDM/ZnO combined with 2% chromate tanning agent were applied in leather tanning process and then the thermal and mechanical properties of the resultant leather were measured. FTIR results revealed that the polymerization reaction of PDM was complete and the carboxyl groups of PDM could react with the hydroxyl groups on the surface ZnO. The crystalline structure of the ZnO nanoparticles in the nano composite was not altered according to the XRD patterns. TEM results showed that nano ZnO was encapsulated on the surface of PDM copolymer chain and nano composites particles dispersed evenly. The results indicated that the tensile strength increased by 11.90% and the tearing strength improved by 23.72%. Compared with PDM, TGA plots showed that the thermal stability of the resultant leather tanned by PDM/ZnO nano composites was improved to a certain extent.