Abscisic acid （ABA） plays a crucial role in plant response to abiotic stress. However， the molecular mechanism by which ABA inhibits the absorption of cadmium （Cd） in Brassica napus seedlings remains to be elucidated. In this study， ‘Youfei 1’ of Brassica napus L. was used as experimental material， and application of 10 μmol/L Cd in Hoagland solution was conducted to simulate cadmium stress. The effects of adding 5 μmol/L ABA under cadmium stress condition， on photosynthetic rate， chlorophyll， carotenoid contents in leaves， cadmium content in above/below ground parts of seedlings and gene expression were analyzed. The results showed that the photosynthetic rate， transpiration rate and stomatal conductance of the leaves were significantly increased， while the contents of chlorophyll and carotenoid were decreased. The contents of cadmium in aboveground and underground tissues were significantly increased under Cd stress condition if compared with that of the control group. The application of ABA could effectively reduce the leaf transpiration rate and stomatal conductance， as well as the contents of cadmium in aboveground and underground parts， and significantly increase the contents of chlorophyll a and carotenoid. Through transcriptome sequencing to identify differentially expressed genes （DEGs）， 514 upregulated and 431 downregulated genes were found. Kyoto Encyclopedia of Genes and Genomes （KEGG） pathway enrichment analysis indicated that DEGs were heavily enriched in pathways such as sucrose and starch metabolism， secondary metabolite biosynthesis， metabolic pathways， and the MAPK signaling pathway， etc. Gene Ontology （GO） functional enrichment revealed that DEGs were enriched in categories such as hemicellulose metabolism， oxidoreductase activity， phenolic compound metabolism， cell wall macromolecule metabolism， and system acquired resistance. The transcriptional trend of selected genes revealed by qRT-PCR is consistent with the transcriptome sequencing results. Further analysis of the differential expression of lignin-related and hemicellulose-related genes （XTH， BXL， PAL， C4H， etc.） in rapeseed leaves under Cd stress revealed that most of these genes were downregulated after abscisic acid treatment. These findings provide a reference for understanding the physiological mechanisms of ABA regulation under Cd stress and contribute to molecular breeding efforts for rapeseed.