Abstract: A nonionic microemulsion(ME) consisted of mixed surfactants named OP-4 ［polyoxyethylene(4)nonylphenol］ and OP-7［polyoxyethylene(7)nonylphenol］, benzyl alcohol, D2EHPA［2-(2-ethylhexylphosphonic acid)］, kerosene as well as HCl solution was prepared.The effects of mass ratio of OP-7 to OP-4,hydrochloric acid concentration,temperature,sodium chloride concentration on the solubilization of HCl solution and the effects of D2EHPA and HCl concentration on phase behaviors were invested.A new membrane-extraction process using the microemulsion as liquid membrane for neodymium extraction in hollow fiber membrane(HFM)was presented for the first time.The results showed out that the content of HCl solution in ME increased with increasing HLB values of mixed surfactants and hydrochloric acid concentrations.But the increase of temperature and NaCl concentration led to a decrease of the content of HCl solution in ME.It also revealed that the WinsorⅡsystem(equilibrium of W/O ME with excess aqueous solution) could form when HCl solution concentration was under 6 mol•dm^-3. While the HCl solution concentration was 7 or 8 mol•dm^-3, however, the Winsor Ⅲsystem(equilibrium of middle ME with both oil and aqueous solution) or the WinsorⅠsystem(equilibrium of O/W ME with excess oil)could form, respectively.As this new membrane-extraction technique was used for the extraction of Nd3+ from 300 mg•dm^-3 feed solution, the extraction percentage reached as high as 95.3% and the concentration in receiving phase was 18.1 fold compared to their initial feed concentration after counter-current extraction with three-modules in tandem.This new membrane system has the advantages of both emulsion liquid membrane and solid membrane extraction.