The measured reduced viscosity-concentration (ηsp/c-c) curves of miscible PPO/PS、 immiscible PMMA/PS mixtures with different composition in toluene all deviate from linear and reveal downward turn in extremely dilute concentration region. Moreover

in the extremely dilute concentration region

the ηsp/c-c curve of immiscible PVC/PS mixture solution shows upward turn in THF

while shows downward turn in DCE. These experimental facts indicate that such viscosity anomaly is not dependent of miscibility

but resulted from wall effects.Regarding the polymer mixture as a single solute

the interference of wall effects on viscosity measurement could be eliminated quantitativle with a proposed theoretical formula. After corrected

the true viscosity data of mixture shows normal linear ηsp/c-c curve in the dilute and extremely dilute concentration region.