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<i>Leucine-rich repeat extensin</i> (<i>LRX</i>) is involved in the regulation of crucial cellular processes, such as cell wall growth and development, as well as signaling. However, the presence of the <i>LRX</i> gene family in <i>Brassica rapa</i> (<i>B. rapa</i>) has not been previously reported. This study identified 17 <i>BrLRXs</i> within the <i>Brassica rapa</i> genome by bioinformatic analysis, and these genes were distributed on seven chromosomes. Phylogenetic and covariance analyses indicate that <i>BrLRXs</i> can be categorized into two distinct branches: the trophic branch and the reproductive branch, with a close relationship observed between <i>BrLRXs</i> and <i>AtLRXs</i>. According to <i>cis</i>-acting element analysis, this gene family is rich in hormone-responsive and stress-responsive elements such as drought-inducibility, abscisic acid, methyl jasmonate, and gibberellic acid responsive elements, suggesting a potential role in abiotic stress response. Transcriptomic, proteomic, and RT-qPCR analyses demonstrated significant up-regulation of <i>BrLRX2</i> and <i>BrLRX6</i> under salt stress, while <i>BrLRX3</i>, <i>BrLRX6</i>, and <i>BrLRX8</i> were significantly down-regulated under osmotic stress. Our analysis of the protein tertiary structure predicts a strong association between LRX proteins and RALF. Protein–protein interaction prediction revealed that LRX interacts with the RALF protein and the receptor FER, which have been previously reported to jointly regulate plant stress responses. We propose that <i>BrLRX6</i> and <i>BrLRX8</i> are implicated in osmotic stress, while <i>BrLRX2</i> and <i>BrLRX6</i> are involved in the modulation of salt stress.