Abstract: Plug flow is a common and complicated flow state in gas--non—Newtonian/two phase flow liquid. Many researches have ever been performed in the world on plug flow of gas--Newtonian liquid. But few researches have been done on that of gas--Non-Newtonian liquid. Through lots of experiments and observation and based on the characteristics of non—Newtonian liquid, the writers have worked out the following: the hydraulic module for the plug flow in horizontal piplines, the flow rate of liquid colume, shovel rate, liquid film flow rate, the frequency and length of liquid colune, the relational expression between the three liquid holdups before finding the pressure drop calculation equation and have the calculated value compared with the experiment data, all of which are obtained on the presmise of such sopposed factors as: 1. The whole pipeline is composed of the flowing L_s units similar to each other; 2. A typical L_R unit contains three parts, which are liquid Colume—L_g, gas colume L_f and liquid film. There is gas both in liquid colune and in liquid film; 3. The the shovel and falling speeis of the flow rates of liquid and film are the same. The colume length is of the fixed value; 4. A wirling area is formed before the liquid colume after the film being shovelled.