Abstract: Objective To explore the relationship between the intensity level of protoporphyrin IX (PpIX) and the concentration of photosensitizer ALA. Methods C. albicans suspension was prepared and incubated with ALA in the dark. The generation of PpIX was observed under a laser confocal microscope. Results After dark incubation, C. albicans and ALA produced fluorescent PpIX. ALA concentration was positively correlated with the intensity of PpIX. When drug concentration reached to 300mmol/L, the intensity of PpIX strength ceased to increase. There was no fluorescent material in control group. Conclusion The inhibitory effect of ALA PDT on C. albicans is closely related to the concentration of the photosensitizer, which provides an experimental base for treatment of C. albicans disease.