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Phase separation dynamic processes in Three-Liquid-Phase System 1 (TLPS), composed of organic oil (P507 extractant), water-soluble polymer (PEG2000), 2 ammonium sulfate and water, with the change of mass composition of phase-forming 3 components were investigated. It was found that dynamic separation of three-layered 4 liquid phases in TLPS is in fact a course of dispersive polymer and organic oil droplets 5 aggregated and separated out respectively from continuous salt aqueous bottom phase. 6Formation rate of organic oil phase was controlled mainly by coalescence rate of 7 dispersed oil droplets, however rate-determining process for formation of polymer middle 8 phase may change from drop sedimentation to coalescence or co-determined by both, 9 when mass composition of the TLPS changed along different operation lines. With the 10 formation of organic oil phase, it becomes another continuous phase, from which 11 dispersive polymer droplets separated out and aggregated into a bulk phase gradually. 12 Phase separation equilibrating time of TLPS, t E , depends on formation rate of the 13 polymer middle phase and its equilibrium volume. A quantitative correlation of phase 14 separation rate of TLPS with its physic-chemical properties was given. The present work 15 promotes further understanding about influence from change in mass composition of 16 phase-forming components in TLPS on three-phase separation dynamic processes. three coexisting liquid phases, different target compounds have different partitioning 6 behaviors in different liquid layers. 2 Application of TLPS has been extended towards 7many areas, such as separation and purification of various biochemicals 3,4 , preparation of 8 natural products 5,6 , treatment of polyphenol waste water 7 and grouping separation of 9 multi-metals 8,9 . All of those works advance such a unique separation method gradually to 10 its maturity. However, this technology has not been used in industrial scale, partially due 11 to the limited engineering knowledge and understanding of phase separation behavior in 12 this system. 13Up till now, most of investigations on TLPS focus only on thermodynamics 14 phase-forming conditions and its stabilization mechanism, without considering its phase 15 separation dynamic process. 10-12 The lack of data in the aspect makes a main hinder for 16 further developing three-liquid-phase partition technique toward its future engineering 17 applications. Our previous work suggested a mixer-settler-mixer three-chamber 18 integrated extractor to conduct three-liquid-phase partitioning processes. 13,14 That work 19 provides a feasible equipment for continuous operation and future industrial scale-up.