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The basic/helix–loop–helix (<i>bHLH</i>) family is a major family of transcription factors in plants. Although it has been reported that <i>bHLH</i> plays a defensive role against pathogen infection in plants, there is no comprehensive study on the <i>bHLH</i>-related defence response in rose (<i>Rosa</i> sp.). In this study, a genome-wide analysis of <i>bHLH</i> family genes (<i>RcbHLHs</i>) in rose was carried out, including their phylogenetic relationships, gene structure, chromosome localization and collinearity analysis. Via phylogenetic analysis, a total of 121 <i>RcbHLH</i> genes in the rose genome were divided into 21 sub-groups. These <i>RcbHLHs</i> are unevenly distributed in all 7 chromosomes of rose. The occurrence of gene duplication events indicates that whole-genome duplication and segmental duplication may play a key role in gene duplication. Ratios of non-synonymous to synonymous mutation frequency (Ka/Ks) analysis showed that the replicated <i>RcbHLH</i> genes mainly underwent purification selection, and their functional differentiation was limited. Gene expression analysis showed that 46 <i>RcbHLHs</i> were differentially expressed in rose petals upon <i>B. cinerea</i> infection. It is speculated that these <i>RcbHLHs</i> are candidate genes that regulate the response of rose plants to <i>B. cinerea</i> infection. Virus-induced gene silencing (VIGS) confirmed that <i>RcbHLH112</i> in rose is a susceptibility factor for infection with <i>B. cinerea</i>. This study provides useful information for further study of the functions of the rose <i>bHLH</i> gene family.