Aiming at investigating the degradation of low concentration tetrabromobisphenol A (TBBPA) in water and toxicity controlling by ozone oxidizing technology, the degradation of TBBPA (concentration: 0.15 mg/L) was carried out by ozone reactor under different values of pH and different dosages of ozone. The variation and controlling of the acute, chronic toxicity, and genotoxicity of the samples during the reaction were investigated, the internal reasons of toxicity were analyzed, and the possible degradation mechanism was proposed. Results show that TBBPA could be completely degraded when pH is 7.0 and ozone dosage is 0.12 mg/L. At the beginning of the reaction, the acute and chronic toxicity increased rapidly, and it was mainly because of the production of more toxic organic intermediates. As the reaction proceeded, the toxic intermediates were further degraded, and both of the acute and chronic toxicities were effectively controlled and the toxicity was controlled more quickly and significantly with the increase of ozone dosage. When the dosage of ozone was 0.12 mg/L, the acute toxicity could be completely controlled within 20 min of reaction, and the chronic toxicity could be controlled to be 0.76 TU within 60 min. After the reaction, the acute and chronic toxicities of the water samples could meet the emission standard. During the reaction, the mutagenic ratios of the samples were all smaller than 2.0, which had no genotoxicity at the genetic level. The analysis of mechanism showed that the degradation of TBBPA by ozonation mainly included the reaction process of debromination, the beta scission, addition, dehydroxylation, methylation, and so on.