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Lignin is an important biological polymer in plants that is necessary for plant secondary cell wall ontogenesis. The laccase (<i>LAC</i>) gene family catalyzes lignification and has been suggested to play a vital role in the plant kingdom. In this study, we identified 45 <i>LAC</i> genes from the <i>Brassica napus</i> genome (<i>BnLACs</i>), 25 <i>LAC</i> genes from the <i>Brassica rapa</i> genome (<i>BrLACs</i>) and 8 <i>LAC</i> genes from the <i>Brassica oleracea</i> genome (<i>BoLACs</i>). These <i>LAC</i> genes could be divided into five groups in a cladogram and members in same group had similar structures and conserved motifs. All <i>BnLACs</i> contained hormone- and stress- related elements determined by cis-element analysis. The expression of <i>BnLACs</i> was relatively higher in the root, seed coat and stem than in other tissues. Furthermore, <i>BnLAC4</i> and its predicted downstream genes showed earlier expression in the silique pericarps of short silique lines than long silique lines. Three miRNAs (miR397a, miR397b and miR6034) target 11 <i>BnLACs</i> were also predicted. The expression changes of <i>BnLACs</i> under series of stresses were further investigated by RNA sequencing (RNA-seq) and quantitative real-time polymerase chain reaction (qRT-PCR). The study will give a deeper understanding of the <i>LAC</i> gene family evolution and functions in <i>B. napus.</i>