Abstract: The extraction behaviour of Zr in 30% TBP-monoalkyl long chain acidic phosphate (MLCAP) -kerosene-HNO3 and MLCAP-kerosene-HNO3 system is studied. The retentive percentage of Zr in organic phase scrubbed by 0.01 mol/1 HNO3 and 5% NaCO3 solution is determined. The mechanism of extraction of Zr by MLCAP is also studied preliminarily. The results indicate that the Zr:MLCAP is equal to 1=2 in the extracted complex. While MLCAP is present in 30% TBP-kerosene-HNO3 system, the distribution coefficient of Zr increases significantly and the tendency toward forming interfacial crude increases. The formed complexes are scrubbed difficultly by 0.01mol/1 HNO3 and 5% Na2CO3 solution and emulsification easily induced. The emulsion extent depends on the concentrations of Zr and MLCAP. The presence of MLCAP with concentration as low as 2×10-4mol/l can lead to serious phase separation problem when the solvent is contacted with 5% Na2CO3 solution even though the concentration of Zr is of trace amount.