Abstract: To achieve the resource utilization and recycling of tobacco waste and reduce its environmental application risks, hydrothermal liquefaction was conducted on the tobacco straws and tobacco leaves at different temperatures to obtain hydrothermal liquid. Hydrothermal liquids derived from corn straws and wheat straws were used as controls to comparatively investigate the effects of hydrothermal liquid from different wastes on plant germination and to analyze the key active organic matter and available nutrients in hydrothermal liquids. Further research was conducted to investigate the effects of tobacco hydrothermal liquids on the activity of second-stage juveniles of root-knot nematodes, the hatching of nematode eggs, and the growth of Fusarium graminearum and Colletotrichum gloeosporioides, to explore the feasibility of tobacco hydrothermal products in the control of plant nematodes and pathogenic fungi. The results showed that the tobacco hydrothermal liquids contained specific active substances small molecule organic acids, cyclic (D-leucine-L-proline) dipeptides, and cyclic (proline-leucine) and high contents of humic acid and nutrients (nitrogen, phosphorus). The hydrothermal liquid of tobacco leaves at 180 ℃ significantly increased the germination index of wild soybeans by 15.24%, presenting a better effect in promoting plant growth. The hydrothermal liquids of tobacco straws and tobacco leaves prepared at 180 ℃ had strong disinfection and control capabilities against root-knot nematodes, with inhibition rate ranging from 98.12% to 99.64%, which was comparable to the disinfection and control ability of the pesticide avermectin against root-knot nematode larvae. The hydrothermal liquids of tobacco straws prepared at 180 ℃ had the most obvious inhibitory effect on the growth of Fusarium graminearum and plant anthracnose fungi, with inhibition rate of 28.24% and 30.11%, respectively. The above results provide solution for the green control of crop diseases.