In this work, the 16S rRNA gene was used to compare the bacterial diversity at thermophilic stage of six different biochar dosage applied SS composting, while compared without biochar added treatment or control. The results showed that biochar amendment affected the structure and succession of bacteria diversity in different ways, and there were 35 prominent genera among all samples displayed in the species abundance heat-map. Among them, Proteobacteria, Firmicutes and Chloroflexi were the main phyla found in genomic libraries from each treatment. The most abundant common genera among the all treatments were Pseudomonas, T78, Acinetobacter and Ureibacillus. In addition, Krona, principal component analysis and beta-diversity indices showed a clear difference in bacterial diversity among the biochar added and control treatments. Finally, our results suggested that Planomicrobium, Paracoccus, Agrobacterium and Devosia could be considered as possible biomarkers symbolic of the thermophilic phase during SS composting. (C) 2017 Elsevier Ltd. All rights reserved.