New amphoteric polyurethane emulsions(AAPU) containing aldehyde group were prepared by polyaddition reaction usingisophoronediisocyanate(IPDI), polytetrahydrofuran glycol (PTMG),2,4-dihydroxybenzaldehyde(DDBA),2,2-dihydroxymethylpropionic acid(DMPA) and N-methyldiethanolamine (N-MDEA) as raw materials. The effects of hydrophilic chain extender and r value on the particle size and stability of emulsions were investigated. The structure of AAPU was characterized by UV and FT-IR. The size, morphology and electrification of latex particle were measured by nano particle size meter, transmission electron microscopy and Zeta potential analyzer. The results show that the products have the expected structure. Average particle size of the as-prepared AAPU is 42.6 nm and its isoelectric point is 5.16 while the value of r and the dosage of DMPA were controlled as 1.2 and 5%, respectively. Furthermore, because the emulsion is amphoteric,it is beneficial to improve the binding capacity between leather and anion wet-finishing materials in the retanning process of non-metallic tanning system as the retanning agent.