A study on two-phase flow characteristics in a coalescence-dispersion pulsed-sieve-plate extraction column of 150mm in diameter was carried out with a working system of 30% tri-butyl-phosphate (TBP) (in kerosene)nitric acid-water. The influence of operation conditions on the holdup of the dispersed phase was investigated. According to the analysis of the experimental data, there was a turning point on the curve of ln(V-s) versus ln(1-phi) under certain pulse intensity. When the holdup is higher than the value at the turning point, the two-phase flow characteristics can be described with the modified Pratt's equation, otherwise a new relation in the form of phi = 1/2.75u(k) (u(c) + 4u(d)) may be used, which is proposed by this study.