Abstract: Using an optical capillary rheometer, the rheological behavior of polyacrylamide(PAM) solutions with different salt concentrations, flowing through capillaries of different diameter(25~150 μm), lengths(40.6~100.1 mm) as well as with or without internal coated-surface at extremely low shear rates have been studied. The results showed that the marked differences rheological behavior of PAM solutions flowing through capillaries of micron diameter are due to the geometrical dimension and nature of the internal wall surface of the capillaries, while the rheological differences occurved in salt-containing PAM solution are due to the electrical property of the solution. Hence, greater internal diameter of the pores and channels and shorter lengths of the channels in the porous media of the oil field are favorable to the oil recovery. And decreasing concentration of sodium ions of PAM solutions could increase the interaction between PAM solutions and oil membrane also favorable to oil recovery.