Bok choy (Brassica campestris ssp. chinensis) is an important vegetable crop native to China and is also one of the leafy vegetables favored by people in Hainan. The high temperature and intense sunlight in Hainan’s summer greatly affect the normal growth and development of bok choy, reducing its yield and quality. At present, research on the growth of bok choy under abiotic stress is mostly focused on heat tolerance, while study on the response of bok choy to strong light stress is relatively scarce. To investigate the molecular regulatory mechanisms of bok choy in response to strong light, this study used the variety ‘Aijiao Huang’ as the research object. We compared and analyzed the physiological indicators, photosynthetic characteristics, and expression levels of response genes in the leaves of bok choy under normal light [300 μmol/(m²·s)] and strong light [1500 μmol/(m²·s)]. Under strong light, dry weight of bok choy significantly increased, and the R/S ratio gradually increased from day 0 to day 10, followed by a significant decrease on day 15. The chlorophyll content significantly decreased in the later stages. Pn, Tr, and Gs significantly increased on day 5 under strong light, and then gradually decreased, while Ci remained relatively stable. Using RNA-seq technology for transcriptome sequencing, a total of 2324 differentially expressed genes (DEGs) were identified. GO and KEGG enrichment analyses revealed 14 DEGs related to photosynthesis and photoprotection mechanisms, and 6 DEGs associated with antioxidant enzyme activity. 8 DEGs were selected for qRT-PCR validation, which were consistent with the transcriptome sequencing results, confirming the reliability of the transcriptome analysis. Strong light had a certain impact on the antioxidant enzyme activity of bok choy. During days 0-5, the activity of SOD, POD, and CAT was induced to increase, while from days 5-15, the activity of SOD and POD gradually decreased, and CAT showed an upward trend. In summary, bok choy may rapidly respond to photosynthesis-related mechanisms and regulate antioxidant enzyme activity under strong light conditions, thereby alleviating the inhibitory effects of strong light on growth and enhancing the seedlings adaptability to strong light.