【Objective】This paper aimed at understanding the relationship between continuous monocropping of vegetable and soil-borne diseases, which will contribute a lot to development of green ecological agriculture. 【Method】Based on the important role of rhizodeposition in plant-soil functional feedbacks, a field experiment was carried out to study incidence variation of root knot nematode diseases and explore its relationships with rhizospheric soil properties, especially composition of rhizodeposits in tomato fields under monocropping for 2, 6 and 8 seasons and the same cultivation management. 【Result】Results show that compared with the plot of 2 season, the plots of 6 and 8 seasons were significantly lower in soil pH (P< 0.05), and significantly higher in concentration of soil total organic carbon and nitrate nitrogen. Root knot index of the tomato and incidence of the root knot nematode disease increased with the monocropping going on. A total of 150 kinds of rhizodeposits were identified with the gas chromatography/time of flight mass spectrometry (GC/TOF-MS) metabolomics, including alcohols, organic acids, amino acids, carbohydrate, terpenes, alkaloids and steroids compounds. Meanwhile, with the monocropping going on, composition and relative contents of the components of the rhizodeposits varied significantly, and the amount and relative abundance of organic acids, such as 3-(3-hydroxyphenyl) propionic acid, salicylic acid, thymol, succinic acid, lauric acid, as main components of the rhizodeposits increased, too. The network architecture analysis of soil chemical properties, rhizodeposits and root knot index shows that the network was reducing in complexity, but intensifying in modularization after continuous tomato monocropping. The compounds in the rhizosphere were quite closely related to soil chemical properties and root knot index of the tomato. Among them, 3-(3-hydroxyphenyl) propionic acid, salicylic acid and succinic acid were negatively related to soil pH, and 3-(3-hydroxyphenyl) propionic acid, salicylic acid and atropine were positively to concentration of soil NO₃^--N. The relationships between root knot index and other nodes were strengthened with the monocropping going on. 【Conclusion】In the plot of 8 season, the root knot index was negatively related to content of lauric acid but positively to concentration of soil NO₃^--N, atropine and ergosterol. The findings shows that the monocropping of tomato aggravates root knot nematode disease, which is closely related to soil chemical properties, especially variation of the rhizodeposits. Therefore, more efforts should be made in future studies, based on screening of key differential compounds, to specify, through simulation of the composition of the rhizodeposits, functions of specific compounds in the rhizosphere and their synergic effects with biological and abiotic factors on incidence of root knot nematode diseases.