A new cyst-forming nematode, Cactodera guizhouensis n. sp., isolated from the roots and surrounding soil of potato in Guizhou, China, is the first species of genus Cactodera found from the potato rhizosphere. The new species was characterized by the L/W ratio of its cyst, being 1.4 ± 0.1 (1.3–1.8), with a fenestral diameter of 17.7–28.7 × 12.3–23.4 μm and being absent vulval denticlest; the stylet length of second stage juveniles is 26.5 ± 1.2 (24.1–29.0) μm, while the tail is 53.4 ± 3.9 (45.0–61.9) μm and the hyaline tail is 25.7 ± 2.4 (21.6–29.8) μm, the lateral field having four incisures and areolation; the eggshell having punctations. The internal transcribed spacer sequences of ribosomal RNA (ITS-rRNA), and sequences of the D2-D3 region of 28S ribosomal RNA (28S-rRNA) from the new species were amplified and sequenced. The phylogenetic tree based on the sequences showed that the new species clustered into a separate clade and could be distinguished from other species in genus Cactodera. A key to the species of Cactodera is also provided in this study.