The uptake and toxicity of silver nanoparticles (AgNPs) to wheat were investigated. The wheat seedlings were exposed to different concentrations of AgNPs suspension in 4h. Oxidative stress and cell membrane damage were observed in roots. The content of malondialdehyde (MDA) and catalase (CAT) increased from (2.9±0.5)nmol/L/mgprot and (8.6±1.2)U/mgprot to (4.9±1.5)nmol/L/mgprot and (12.4±1.2)U/mgprot. The addition of L-cysteine reduced the toxicity of AgNO3 to wheat and decreased the dissolved uptake rate constant of AgNO3 from (275.4±12.3)L/(kg∙h) to (210.8±11.2)L/(kg∙h). In contrast, L-cysteine did not affect the toxicity of AgNPs to wheat, and the dissolved uptake rate constant did not differ significantly before and after the addition of L-cysteine [i.e., (12.6±0.8) vs (11.2±0.6)L/(kg∙h)]. The results suggested that not only the released Ag+ from AgNPs, but also the particles themselves contributed to the bioavailability and toxicity of AgNPs. Furthermore, the dissolved uptake rate constants from different species of Ag in the presence of L-cysteine (i.e., dissolved Ag+, AgNP particles, and Ag-cysteine) were calculated, and dissolved Ag+ exhibited the highest bioavailability [(275.4±12.3)L/(kg∙h)], followed by Ag-cysteine complex [(210.8±11.2)L/(kg∙h)] and finally the nanoparticles [1.6L/(kg∙h)]. A model described the uptake process of AgNPs were thus established. The predicted overall uptake rate constants were comparable to that observed in the experiment, which validated the success of the model in describing the uptake of AgNPs. © 2018, Editorial Board of China Environmental Science. All right reserved.