Phosphor sedimentation is a key factor affecting the light quality and optical consistency of white light-emitting diodes (LEDs). Herein, a detection method based on optical coherence tomography (OCT) is proposed to realize rapid, nondestructive detection of phosphor sedimentation in white LEDs. For this purpose, a white LED was imaged by an OCT system. Subsequently, the OCT and section images of the LED were compared, and the quantity distribution and sediment morphology of phosphor were analyzed. In addition, an algorithm was developed to extract the area fraction of phosphor from the OCT images based on the relationship between the quantity and area fraction of phosphor and the variations in quantity distribution during sedimentation. Furthermore, the relationship between the area fraction of phosphor and the degree of phosphor sedimentation was studied. The experimental results show that OCT can accurately determine the phosphor sediment morphology in white LEDs and that the area fraction of phosphor observed in the OCT images can quantify the degree of phosphor sedimentation. This method can meet the detection requirements of phosphor sedimentation in white LEDs and can be used for their quality testing and packaging process research.