Abstract: A pure Benzotriazoles (BTs) degrading culture isolated under aerobic condition was investigated. Analysis of the 16S rDNA sequence and database indicated that the closest strain was the Pseudomonas.taiwanensis BCRC 17751, and this isolated strain was named as Pseudomonas.BTs. The isolated strain was able to degrade three BTs (BTri, 5-TTri and CBT) with different removal rates in the presence of external carbon source but could not utilize BTs as sole carbon source. The effects of 11 external carbon sources used as growth substrate on the co-metabolism of BTs by Pseudomonas.BTs were tested. The feed mass ratio (m_C:m_BTs) of 1 000:1 would be better for co-metabolism of BTs than 100:1. Among all 11 substances, glucose, sodium glutamate and ethanol were the most beneficial to co-metabolism of BTs by Pseudomonas.BTs, whereas the co-metabolism of BTs did not happen at all when phenol, maltose, humic acid or starch served as the source of external carbon. The biotransformation products (TPs) of BTri, 5-TTri and CBT by Pseudomonas.BTs were identified using ultra high-performance liquid chromatography coupled with a quadrupole-time-of-flight high-resolution mass spectrometer (UHPLC-QToF-MS). The results indicated that the three BTs shared relatively consistent transformation pathways including isomerization, methylation and other similar functional group addition reactions. Most TPs were reported for the first time. The results obtained in this experiment may provide basic information for understanding the mechanism of biotransformation of BTs as well as the optimization of BTs removal.