Environmental abiotic stresses limit plant growth, development, and reproduction. This study aims to reveal the response of Brassica napus to salt stress. Here, transcriptomics, metabolomics, and proteomics analysis were performed on 15 Brassica napus leave samples treated with salt at different times. Through functional enrichment analyzing the differentially expressed genes (DEGs), differential metabolites (DMs) and differentially expressed proteins (DEPs), the key factors that dominate Brassica napus response to salt stress were identified. The results showed that the two key hormones responding to salt stress were Abscisic acid (ABA) and jasmonic acid (JA). Salt stress for 24h is an important milestone. Brassica napus adjusted multiple pathways at 24h to avoid over-response to salt stress and cause energy consumption. The increased expression in BnPP2C is tangible evidence. In response to salt stress, JA and ABA work together to reduce the damage caused by salt stress in Brassica napus. The increased expression of all BnJAZs after salt stress highlighted the function of JA that cannot be ignored responding to salt stress. In addition, some metabolites, such as N-acetyl-5-hydroxytryptamine, L-Cysteine and L-(+)-Arginine, play a critical role in maintaining the balance of ROS. Proteins like catalase-3, cysteine desulfurase, HSP90 and P450_97A3 were the most critical differential proteins in response to salt stress. These findings of this study provide data support for Brassica napus breeding.