Abstract: Abstract: In this paper, physiological and biochemical mechanisms of melon autotoxicity induced by plant aqueous extracts and root exudates were analyzed. The results showed that root activity showed a downward trend with the concentration of melon extracts and root exudates rising; the free water content declined, the bound water content raised; chlorophyll a, chlorophyll b and carotenoid content decreased; activated oxygen increased; proline content decreased firstly and then increased; soluble sugar and soluble protein content increased firstly and then decreased; ascorbic acid content had no obvious changing in extracts conditions, and decreased gradually in root exudates conditions; glutathione content decreased in extracts conditions, and increased in root exudates conditions.