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The leakage of landfill leachate (LL) into environmental media would be happened even in the sanitary/controlled landfill, due to the deterioration of geomembrane and the blockage of drainage system after long-term operation. Considering the complex composition and high concentration of pollutants in LL, its toxicity assessment should be conducted as a whole liquid contaminant. Therefore, the impacts of LL on Caenorhabditis elegans (C. elegans) were investigated under the condition of different exposure time and exposure volume fraction (EVF). The stimulating effects on locomotion behavior and growth of C. elegans were observed after acute (24 h) exposure to LL, which were increased firstly and then decreased with the increase of EVF. Meanwhile, the intestinal barrier was not affected by LL, and levels of reactive oxygen species (ROS) and cell apoptosis significantly decreased. However, stimulation and inhibition effects on locomotion behavior and growth of C. elegans were observed when subacute (72 h) exposure to 0.25%–0.5% and 1%–4% of LL, respectively. The intestinal injury index and levels of ROS and cell apoptosis significantly increased when EVF were 2% and 4%. Although the acute exposure of LL had resulted in obviously biological adaptability and antioxidant defense in C. elegans , the protective mechanisms failed to be induced as the exposure time increased (subacute exposure). The toxic effects were confirmed by the down-regulation of genes associated with antioxidant defense and neurobehavior, accompanied by the up-regulation of intestinal injury and cell apoptosis related genes. Moreover, the disturbance of metabolic pathways that associated with locomotion behaviors, growth, and antioxidant defense provided good supplementary evidence for the confirmation of oxidative stress in C. elegans. The research results verified the potential of C. elegans as model organism to determine the complex toxic effects of LL. [Display omitted] • Acute expose to landfill leachate (LL) can active antioxidant defense of C. elegans. • Protective mechanisms failed to be induced when subacute exposure to LL. • The toxic effects of LL were confirmed by the expression change of related genes. • Disturbances in metabolic pathway confirm oxidative stress response of C. elegans. • Metabonomic results verify the response of phenotypic and molecular indexes. [ABSTRACT FROM AUTHOR]