This study provides a parallel cytotoxicity study of water-soluble single-walled carbon nanotubes and fullerene C70(C(COOH)2)4-8 on Nicotiana tabacum BY-2 cells. After BY-2 cells were treated with single-walled carbon nanotubes or C70(C(COOH)2)4-8, the cells adopted a shrunken morphology and exhibited lower proliferation rate. Fluorescence imaging of the treated cells revealed increased reactive oxygen species generation, abnormal mitochondrial distribution, decreased mitochondrial activity, and impaired actin cytoskeleton arrangement. However, no obvious cells death was induced by either single-walled carbon nanotubes or C70(C(COOH)2)4-8. Compared with single-walled carbon nanotubes, C70(C(COOH)2)4-8 exerted more serious adverse effects on BY-2 cells.