The available experimental data, Vishnev et al. [6], implies that the widely used homogenous equilibrium model and the Martinelli–Nelson equation do not map correctly the pressure drop data for horizontal liquid helium two phase flow particularly in cases for high vapour fraction. Hence, considering the empirical nature of Martinelli–Nelson equation, suitable parameters and terms have been suggested so that, the pressure drop can be better predicted. The proposed equation being a third order in ‘x’ (vapour fraction) is more accurate to predict the characteristic behavior of liquid helium two phase flow as observed in experiments [6], Mamedov et al. [7], and Deev et al. [8], which the available equations are unable to predict.