Abstract: The kinetic energy loss and drainage effect of glass capillary viscometer are treated theoretically. These two correction factors interrelate closely and can not be separated with each other. The representative equation of glass capillary viscometer for measuring liquid viscosity may be written as
η/ρt=A~*-(B~*/t~2)-(C~*/t~4)
in which A*, B* and C* are instrumental constants. The numerical factor m of the kinetic energy correction term in the Poiseuille-Hagenbach equation is raised from the effect of adhering of liquids on the wall of the viscometer and may be represented by
m=1+(C~*/B~*t~2)
Therefore, the fact of ascending m with increasing Reynold number will be explained. Equations for calculating the relative viscosity of polymer solution and method for determining the instrumental constants are given.