The pathways of bromate formation during ozonation of bromide-containing lake water were investigated. The results showed that bromate formation was inhibited efficiently by adding t-butanol which is an ·OH scavenger, or promoting (bi)carbonate alkalinity. It was also suggested that addition of H2O2 yielded different results. Bromte formation was restricted when H2O2/O3 mole ratio was 0.5:1, while increase of bromate formation occurred when H2O2/O3 mole ratio was more than 1:1. An O3 dose of 4.5mg/L was applied during such lake water ozonation. It was suggested that the main pathway of bromate formation was indirect pathway, the direct pathway, in contrast, was recognized as a less important pathway due to the bromate formed in this pathway accounted for only 8% of total production.