There are two main causes of dark yellow teeth, one is exogenous staining of teeth and the other is endogenous staining of teeth. Exogenous staining of teeth is mainly caused by poor oral hygiene, serious smoking and tea drinking, and the accumulation of black tartar and pigmentation on the tooth surface. The treatment is ultrasonic scaling, sandblasting and polishing, and when the dirt and pigmentation on the tooth surface are removed, the yellowing of teeth will be significantly improved. Endogenous tooth coloring, on the one hand, is caused by physiological factors, such as congenital yellow teeth or ageing-induced yellow teeth; on the other hand, it is caused by pathological factors, such as tetracycline teeth, fluorosis, dead pulp teeth, endogenous tooth coloring can be bleached by cold light whitening method. Therefore, yellow teeth are not a physical problem, but mostly caused by local factors in the oral cavity. After treatment with appropriate methods, the shade of the teeth will be improved, in addition to maintaining a good oral hygiene environment on a daily basis to prevent the recoloration of teeth.