Objective To evaluate the adoption of carbon nano-particle in the pathologic examination of lymph node for lower rectal cancer. Methods Sixty consecutive patients with rectal cancers located at or below the peritoneal reflection were randomly allocated to the routine method group or the group using carbon nano-particle. Resultsof pathologic examination were compared. Results Altogether, 1 070 lymph nodes were examined from the 2 study groups. The average examined number of the carbon nano-particle group was (20.2±4.9)/case, which was significantly higher than the other group 〔(15.4±6.8)/case〕, P=0.003. More tiny lymph nodes were examined in the nano-particle group (P=0.029) and more metastases were proved from the lymph nodes dyed by nano-particle (P=0.000). The majority of examined lymph nodes were located along the superior rectal vessel and its branches. ConclusionAdoption of nano-particle in pathologic examination of rectal cancer surgery can increase the examined number of lymph nodes, while detect small nodes harboring cancer, thus ensuring the correctness of pathologic report. The distribution of mesorectal lymph nodes underlines the execution of TME principle in dissection.