[Objective] Riemerella anatipestifer is a Gram-negative bacterium infecting ducks, causing serious economic losses to the duck industry. After infection,R.anatipestifer regulates gene expression to adapt to the 42 ℃ body temperature of ducks. To identify the adaptation mechanism ofR.anatipestifer CH-1 in ducks, we sequenced and compared the transcriptomes ofR.anatipestifer CH-1 at 37 ℃ and 42 ℃. [Methods] R.anatipestifer CH-1 was cultured to the exponential growth phase at 37 ℃ and then subjected to heat stress at 37 ℃ and 42 ℃, respectively, for 1 h. The cells were then collected for the extraction of total RNA. The raw transcriptome data of the bacteria cultured at 37 ℃ and 42 ℃ were obtained by transcriptome sequencing, and differentially expressed genes (DEGs) were screened. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses were carried out for the DEGs. The genednaK involved in the response to heat stress was selected for preliminary functional identification. [Results] A total of 234 DEGs were screened out, including 169 genes with up-regulated expression and 65 genes with down-regulated expression. The GO enrichment analysis showed that the DEGs were mainly enriched in the nucleotide metabolic process, glycosyl compound metabolic process, and core RNA polymerase binding transcription factor activity. The KEGG enrichment analysis indicated that the DEGs were mainly involved in oxidative phosphorylation, ribosomes, and bacterial secretion systems. The deletion ofdnaK impaired the growth ofR.anatipestifer CH-1 at 42 ℃, compared with that at 37 ℃. [Conclusion] Compared with that at 37 ℃, the growth ofR.anatipestifer CH-1 was not affected at 42 ℃. The strain up-regulated or down-regulated the expression of heat shock response proteins and other factors to cope with heat stress.