The extraction and separation of heavy rare earths (REs) using newly synthesized α-aminophosphonic acid extractant 2-ethylhexyl 3-(2-ethylhexylamino)pentan-3-yl phosphonic acid (HEHAPP, HA) in n-heptane has been investigated from chloride medium.The extraction stoichiometries of lanthanum, gadolinium, yttrium and lutetium have been determined in detail with the method of slope analysis.The extracted complexes, equilibrium constants (Kex), separation factors and loading capacity of HEHAPP have been studied.The stripping behaviors of heavy RE by HC1, HNO3 and H2SO4 have been examined.Results showed that the extracted complexes were determined to be REA3.HEHAPP was found to be a potential extractant for separating heavy RE(Ⅲ), and favorable separation factors of adjacent heavy RE(Ⅲ) βY/Ho, βEr/Y, βTm/Er, βYb/Tm and βLu/Yb were 1.87, 1.36, 3.21, 3.22 and 1.93 respectively when extracted from a binary system at proper acidities.The loading capacity of HEHAPP for Ho, Er,Yb and Lu increased in the order Ho < Er < Yb < Lu and were 0.201, 0.205, 0.216 and 0.229 mol/L, respectively.Among the three inorganic acids, HCl was the most effective stripping agent.