Parameters in the typical correlations for volume fraction of gas-phase and frictional pressure drop of developed steady gas-liquid two-phase flows in pipes have been studied. The distribution parameter in the Drift-flux model for the volume fraction of gas-phase has been expressed by the seven non-dimensional groups composed of input physical quantities. The parameter used in correlation for frictional pressure drop by Lockhart-Martinelli and Chisholm has been expressed by the seven non-dimensional groups composed of input physical quantities and imaginary pressure drops. By using these new expressions, these flow characteristics can be calculated with higher precisions and the effects of various input physical quantities on them are obtained.