A novel constant interfacial area cell (NCIAC), by spatially separating the agitation from liquid flow circulation of organic and aqueous two phases, was suggested to obtain detailed kinetic data for Er(III) extraction from chloride medium by 2-ethyl-hexyl-phosphonic acid mono-(2-ethylhexyl) ester (EHEHPA). Different from the traditional Lewis cell and the constant interfacial area cell with laminar flow, the concentrations of Er(III) in organic and aqueous two phases were uniform, and the stability of the interfacial area between the two phases could be controlled effectively. Therefore, the special requirements for the design of agitators in the traditional Lewis cell and the constant interfacial area cell for minimizing the influence of diffusion resistance could be avoided. Experimental results indicated that the extraction kinetics was mainly affected by the aqueous flowrate, interfacial area between organic and aqueous two phases, and the aqueous pH values. An extraction kinetic equation was suggested based on the experimental data. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.