The motion and interactions of three equal-interval parallel bubbles in non-Newtonian fluids were numerically simulated by volume of fluid method (VOF), in which the continuous surface tension model and the power-law model were adopted to represent surface tension and rheological properties of non-Newtonian fluids, respectively. The computational method was validated by the comparison of the processes of coalescence of two in-line bubbles and rising of two parallel bubbles between experiment and simulation. This method was then applied to study the effect of initial bubble diameter, initial horizontal bubble interval and rheological properties of non-Newtonian fluids on lateral coalescence and rising of three parallel bubbles. The dimensionless critical horizontal interval of bubble coalescence was obtained under different physical property conditions. The critical horizontal interval of bubble coalescence decreases with the increase of initial bubble diameter and flow index of non-Newtonian fluids. When the initial horizontal bubble interval is less than the critical horizontal interval of bubble coalescence, three bubbles will coalesce into a bigger bubble. The coalescing bubble could breakup into two identical daughter bubbles when the initial bubble diameter was increased or the flow index of non-Newtonian fluids was decreased. Three parallel bubbles rising in non-Newtonian fluids will experience repulsive interactions once the initial horizontal bubble interval is greater than the critical horizontal interval of bubble coalescence, the horizontal bubble interval increased gradually owing to the repulsive effect, while the vertical distance between bubbles varied dramatically for spherical bubble and ellipsoidal bubble due to the differences of their flow field structures. (C) 2013 Elsevier Ltd. All rights reserved.