For further understanding of interaction between phosphatidylcholine and hydroxyl-terminated polybutadiene (HTPB) in styrene solution, the effect of phosphatidylcholine on the rheological properties of HTPB-styrene solution was studied by viscometric method. The viscosity changing factor(|C|) was used to characterize the degree of molecular interaction between phosphatidylcholine and HTPB. In this approach, the blending behavior of phosphatidylcholine and HTPB in mixed solution system was further discussed. Meanwhile, the effect of the relative contents of phosphatidylcholine and HTPB on the interaction degree was researched. Results show that the solution viscosity increases with the increasing of phosphatidylcholine. And the solution exhibits a more remarkable non-Newtonian behavior. The flow activation energy (E) first increases and then decreases, while the interaction degree between phosphatidylcholine and HTPB first decreases and then increases. |C| increases to the maximum value of 0.165 and E/R decreases to the minimum value of 1004.9 as phosphatidylcholine content reaches to 0.053.