A novel labyrinth flow bubble photoreactor (LBPR) was designed and the model of multiple mixed flow reactors (MMFRs) in series was established to describe the behavior of the LBPR during batch recirculation system of low concentration organic pollutant degradation by photocatalysis. This model was developed by the mass balance combining the rate equation of the photocatalytic reaction. The influence of the structural parameters, such as the number of baffle plates, the space between the baffle plates and the height of liquid exit in the reactor, on the photocatalytic degradation of organic pollutant was mainly investigated. The relationships between the final conversion rate and the liquid rate, liquid volumes, light intensity and catalyst amounts were also predicted by this model. TiO2 was immobilized on quartz glass particles by sol-gel method and used as the photocatalysts; the degradation experiment of methyl orange (MO) was performed in a 21 LBPR reactor to validate the above model. The experimental results showed that the removal rate of MO could reach 100% with 12 baffle plates and 4 cm height of liquid exit after 1.5 h treatment when the flow rate was 0.0111 m(3) h(-1) and the particle catalysts was 4.8 g l(-1). The prediction of the model is consistent with the experimental results. This research provides exploratory work for the design of a novel commercial scale photocatalytic reactor. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.