||Previous experiments observed auto-acceleration in the etherification of glycerol with isobutene. This article engaged to uncover the reason for this phenomenon via investigating the heterogenicity, including liquid-liquid phase equilibrium and liquid-liquid-solid mass transfer, of the reaction system. Phase behavior analysis showed that the reaction mixture separates into two liquid phases during the whole course of the reaction. The produced mono ethers of glycerol thermodynamically promote the homogenization of the two liquid phases. The modeling results of liquid-liquid-solid mass transfer indicated that the resistance of mass transfer is insignificant during the reaction. The bulk compositions of the two liquid phases are very close to their corresponding equilibrium compositions. An increase of isobutene concentration in the reaction phase is believed to lead all reactions speeding up.