Bubbly liquid exists widely in industrial fields, so the detailed understanding of physical properties of bubbly liquid is significant for improving product quality and for strengthening industrial processes. In this paper, in order to understand the modulation mechanism of bubbles on the liquid-phase apparent viscosity, based on the two-dimensional parallel plate model, the effect of dispersed bubbles on the liquid-phase apparent viscosity was deeply investigated with the volume of fluid (VOF) method combined with a dynamic mesh. The influence of the volume fraction, the capillary number, and the distance between bubbles on the liquid-phase apparent viscosity was studied in detail for the dispersed bubbly liquid. The present studies show that both the capillary number and the volume fraction have a great effect on the liquid-phase apparent viscosity; for the cases with the same volume fraction, the bubble injection causes the decrease of the relative viscosity of the liquid phase when the capillary number of bubbles is relatively large (Ca>0.5), and the larger the volume fraction is, the more sharply the relative viscosity of the liquid phase decreases. However, under the same volume fraction, the relative viscosity of the liquid phase increases when the capillary number of bubbles is relatively small (Ca<0.5), and the higher the volume fraction is, the more obviously the relative viscosity of the liquid phase increases. In addition, as the volume fraction increases, the bubble-bubble interaction becomes very important, and the contribution of each bubble to the shear stress (i.e. the liquid apparent viscosity) decreases.