The study aims to investigate the physiological mechanism of biochar with nitrogen application on mitigating the germination of ‘Paulownia 1201’ seeds under Cd stress and to provide a reference for the application of biochar and nitrogen for remediation of the Cd-contaminated soil Taking the seeds of ‘Paulownia 1201’ as the test material we investigated the effects of different concentrations of the Paulownia biochar treatment solution with nitrogen on the germination characteristics antioxidant levels osmotic substances and nutrient levels of seeds under Cd stress 1 Biochar nitrogen and their combinations significantly enhanced the germination potential germination rate germination index and vigor index of the seeds As the concentration of the treatment solution increased the length of young shoots root length fresh weight and free amino acid content were increased reaching their maximum values at 5 g L biochar while the starch content showed a decreasing trend 2 When biochar or nitrogen was applied alone the contents of GR activity Pro and MDA were decreased while H₂O₂ did not change significantly The lowest contents of Pro and H₂O₂ were observed at 5 g L SS and SP were increased with the increase in treatment concentrations Additionally the activity of APX was initially increased and then decreased with the germination time 3 When biochar and nitrogen were applied together the activities of APX and GR enzymes reached their maximum values MDA and H₂O₂ were decreased while Pro was increased slightly The overall improvement effect was Biochar with nitrogen>biochar>nitrogen The application of biochar and nitrogen can enhance the antioxidant and osmoregulation ability of Paulownia seeds promote the accumulation of nutrients and significantly promote seed germination In particular biochar combined with nitrogen is the best treatment