The dynamics of multiple horizontal bubbles rising from different orifice arrangements in shear-thinning fluids was simulated numerically by three-dimensional Volume of Fluid method. The effects of bubble size, rheological properties of shear-thinning fluids, and orifice structure arrangements on multiple bubbles interaction and coalescence were analyzed, and the mechanisms of bubble coalescence and breakup were fully discussed and elucidated. The variation of bubble rising velocity during coalescence process and freely rising processes for different orifice arrangements was also deeply investigated. The critical initial horizontal intervals for coalescence of multiple horizontal bubbles with various orifice arrangements were attained by simulation, which could serve as the critical criterion of bubble coalescence or noncoalescence. Furthermore, the critical bubble interval was predicted based on the film drainage model, the prediction accords well with the simulation result and is quite conducive for the design and optimization of perforated gas-liquid contact equipment. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 3528-3546, 2015