Abstract: The study of gas-liquid contact regimes on Hy-contact valve tray shows that for ordinary operation conditions the dispersion structures are. in spray, mixed froth and froth regimes respectively. The mixed froth regime occurs most commonly within the normal vapor-liquid load range. Spray is likely to be promoted by a high vapor load, low liquid rate and low weir height. The distribution of spray-froth in the mixed froth regime is different at different places of the tray and varies with the liquid loads. The interrelationship between the regimes, liquid entrainment ratios and clear liquid height is obtained and two inversion points are defined. The mechanism and the physical model of the contact regimes are discussed and tentative correlations of the phase inversion points composed of dimensionless groups are proposed.