Abstract: A mathematical model of ethylene oxide synthesis in three-phase bubble column slurry reactor is presented. It accounts for axial dispersion of liquid phase, settling-dispersion of catalyst and gas-liquid mass transfer. The effects of parameters, such as superficial gas velocity,height of three-phase slurry bed,diameter of reactor and molar fraction of ethylene in the feed syngas on axial distribution of catalyst concentration in the reactor,molar fraction of ethylene oxide in exit gas,selectivity of ethylene oxide and space-time yield were examined. Reasonable design parameters, such as the size of industrial reactor, superficial gas velocity,selectivity of ethylene oxide and space-time yield were predicted and useful information for the design of three-phase bubble column slurry reactor of ethylene oxide synthesis was obtained.