Copolymers p (DMAE-co-[HVIM]Br) were prepared by free radical polymerization using 1-dodecyl-3-vinylimidazole bromide [HVIM] Br and dimethylaminoethyl methacrylate (DMAEMA) as raw materials and azodiisobutyronitrile (AIBN) as initiator. Namely,[HVIM] Br was synthesized from1-bromododecane and an ionic liquid such as 1-vinylimidazole. Then amphoteric polymer p (DMAE-co-[HVIM]Br) PS was synthesized by quaternization of copolymer with 1,3-propionic lactone. The structure of the products were characterized by infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H-NMR). Then the combination of amphoteric polymer and castor oil in different proportions was applied to the fatliquoring process of leather. The structure and morphology of the wet white leather after fatliquoring were studied by SEM and ultra-deep field microscopy. The softness and physical and mechanical properties of the leather after fatliquoring were measured. The results showed that the softness and physical and mechanical properties of the leather treated with the synthesized amphoteric polymer were improved.