The mandibular canine usually has a single root with a single canal. It is rarely to see a mandibular canine with two roots and two toot canals. A case of a patient who has a right mandibular canine with two roots and two root canals was reported. Cone beam computed tomography (CBCT) comprehensively demonstrated the root canal system and especially provided the information of canal varieties and complex canal before operation. CBCT can improve the discovery rate of canal varieties, guide root canal treatment and prevent missed roots in tooth extraction.