In two-phase flow, void fraction plays an important role in the pressure gradient calculation and the flow pattern analysis, while the distribution parameter C0 and drift velocity ugm are crucial parameters in the establishment of drift flux void fraction correlation. Since the distribution parameter and drift velocity in the constitutive equation cannot reflect the influence of gas–liquid velocity and pressure in most existing correlations, theoretical and experimental studies are carried out to solve these problems in this study. The electromagnetic wave coaxial line phase sensor is designed for void fraction measurement, and the horizontal slug flow experiments (63 data points) have been conducted in a stainless steel tubular test section with an inside diameter of 50.0 mm. A comparison of the performance of thirteen existing drift-flux predictive correlations based on current and literature data (with different pressures (0.1–0.6 MPa) and pipe diameters (19–101.6 mm)) is made. Based on comparative analysis, the L-M parameter X, the liquid mass quality ratio to gas mass quality (1-x)/x and superficial velocity um are chosen to optimize the structure of existing models. A new drift flux correlation that could handle different phase velocities and system pressure is proposed. Experimental results indicate that the mean absolute percentage error (MAPE) of the distribution parameter and drift velocity correlations are 5.88 % and 27.37 %. The MAPE of the drift flux void fraction is 6.98 % (current data) and 11.07 % (literature data), respectively.