Abstract: In order to clarify the toxic effects of biochar on the growth of pepper, the effects of biochar extract solutions from different sources (rice straw, miscellaneous tree, cow dung and sludge) on the germination and seedling growth of pepper seeds were studied by using the biochar extract solution culturing method. The results showed that the extract solution of woody biochar (MZBC) promoted the germination of pepper seeds, while the extract solutions of sludge-derived biochar and cow dung biochar significantly inhibited the germination of pepper seeds, and the inhibitory effect would continue when the pepper grew into the seedling stage. Additionally, the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in seedling roots treated with sludge-derived biochar (WNBC) and cow dung biochar (NFBC) extract solutions were significantly increased, and the content of malondialdehyde (MDA) in the roots of seedlings treated with cow dung biochar extract solution increased significantly, indicating that the cell membrane integrity of seedling roots was destroyed and the lipid peroxidation occurred under the treatment of cow dung biochar, which showed obvious toxic effects. Meanwhile, the contents of MDA in leaves treated with four biochar extract solutions were all not higher than that under the CK treatment. The above results showed that compared with leaves, the roots were more sensitive to the external environment and more vulnerable to damage.