<p>Brassinosteroids (BR) are a kind of plant hormones in promoting plant growth and development. Adventitious rooting is a critical route for asexual reproduction in plants. However, the function of BR in adventitious rooting is still not clear. We explored the role of BR in adventitious rooting in marigold, results showed that BR promoted adventitious rooting in a dose-dependent manner, with 1µM 2, 4-table brassinolide (EBL) being the most effective concentration. In contrast, 0.5 µM brassinolide biosynthesis inhibitors brassinoazole (Brz) significantly inhibited root development. Peroxidase (POD) activity gradually increased in EBL-treated explants (1µM EBL) from 12 to 48&#xa0;h. Polyphenol oxidase (PPO) activity in explants exposed to EBL was decreased at 6–36&#xa0;h. PPO level in EBL-treated explants at 48&#xa0;h was significantly higher than that in untreated explants (the control), while PPO activity in Brz-treated explants (0.5µM Brz) significantly decreased at multiple time periods. Additionally, the overall level of indoleacetic acid oxidase (IAAO) activity was higher than that of the control and Brz. EBL increased zeatin (ZT), indole-3-acetic acid (IAA) and gibberellic acid (GA₃) content, and decreased abscisic acid (ABA) content. However, Brz had the adverse effect during rooting compared with EBL. In summary, BR may promote adventitious rooting through enhancing rooting-related enzyme activities (PPO, POD and IAAO), some plant hormone contents (ZT, IAA and GA₃) and carbohydrate and protein contents (total sugar, sucrose, glucose, starch and soluble protein content), and reducing endogenous ABA levels. This study provides an important basis for further understanding of the mechanism of BR on adventitious rooting.</p>