The performance of a 3 mm bubble column reactor with multiple micro-bubbles and immobilized Fe3+/TiO2 photocatalyst was studied by photocatalytic degradation of MB. The bubble flow with multiple micro-bubbles was realized by a novel gas-liquid distributor, which can disperse a single bubble with diameter of 1481 mu m into multiple micro-bubbles with average diameter of 432 mu m. The idea of discretization was introduced to build the radiation model and obtain the distribution of radiation flux density of absorbed light. Reaction kinetics model containing UV-light and visible light in which mass transfer was included was built. Experimental data were fitted with the model and the kinetics parameters were obtained. The influences of reaction conditions show that multiple micro-bubbles play an important role in improving mass transfer coefficient (k(L,mB)), surface concentration ([C-s,C-MB/C-MB](av)) and reaction rate constant (k(r)). When the gas holdup epsilon(G) increases from 0.0015 to 0.0110, the kr increases about 2.7 times. Compared with the single bubble flow, the k(L,mB) and k(r) of bubble flow with multiple micro-bubbles increase about 2 times, and the [C-s,C-MB/C-MB](av) also increases 2.25%. The quantum efficiency of visible light is much less than that of UV-light, which means that the utilization of visible light should be further improved.