When rectal cancer causes inguinal lymph node metastasis, it is not based on the size of lymph nodes, but when cancer cells are found in pathological examination of lymph nodes, it is lymph node metastasis. Rectal cancer is a common malignant tumor of intestinal tract, if not treated at early stage, it is easy to have local infiltration and distant metastasis. Generally, distant metastasis is dominated by blood metastasis, such as liver metastasis, and lymphatic metastasis, such as inguinal lymph node metastasis, is rare. For inguinal lymph node metastasis of rectal cancer, cancer cells are mainly transferred through pelvic lymphatic system, according to different regional lymph node metastasis, we can judge the distant metastasis of rectal cancer, so as to guide the subsequent treatment accordingly. If rectal cancer causes inguinal lymph node metastasis, one should receive appropriate treatment as early as possible to control the development of the disease so as to improve the survival rate.