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<i>Brassica napus</i> and its diploid progenitors (<i>B. rapa</i> and <i>B. oleracea</i>) are suitable for studying the problems associated with polyploidization. As an important anti-stress protein, RCI2 proteins widely exist in various tissues of plants, and are crucial to plant growth, development, and stress response. In this study, the <i>RCI2</i> gene family was comprehensively identified and analyzed, and 9, 9, and 24 <i>RCI2</i> genes were identified in <i>B. rapa</i>, <i>B. oleracea</i>, and <i>B. napus</i>, respectively. Phylogenetic analysis showed that all of the identified <i>RCI2</i> genes were divided into two groups, and further divided into three subgroups. Ka/Ks analysis showed that most of the identified <i>RCI2</i> genes underwent a purifying selection after the duplication events. Moreover, gene structure analysis showed that the structure of <i>RCI2</i> genes is largely conserved during polyploidization. The promoters of the <i>RCI2</i> genes in <i>B. napus</i> contained more <i>cis</i>-acting elements, which were mainly involved in plant development and growth, plant hormone response, and stress responses. Thus, <i>B. napus</i> might have potential advantages in some biological aspects. In addition, the changes of <i>RCI2</i> genes during polyploidization were also discussed from the aspects of gene number, gene structure, gene relative location, and gene expression, which can provide reference for future polyploidization analysis.