OBJECTIVE To investigate the morphological characteristics of Dermatophagoides farinae at different developmental stages. METHODS The cultured D. farinae was isolated, and the external morphological features of mites at various developmental stages were observed using scanning electron microscopy (SEM), including egg, larva, nymph and adult stages. RESULTS The D. farinae egg appeared a long oval shape, and the larval mites had three pairs of legs. The nymph had four pairs of legs and underdeveloped genital pores containing genital setae and anal setae, and adult mites appeared long and oval in shape, with decorative patterns on epidermis, and had four pairs of legs. In male adult mites, remarkable thickening of the leg I and thicker and longer leg III than the leg IV were seen, and ventral genital regions were found between the basal segments of legs III and IV; the anus was surrounded by a circular peri-anal ring, with a pair of anal suckers and anal setae within the ring. In the female adult mites, slender legs III and IV with an equal length were seen, and a "λ-shape" genital hole was observed on the ventral surface, with a crescent-like genital plate in the anterior part, and the anus appeared a longitudinal slit. CONCLUSIONS An SEM observation of the external morphology of D. farinae provides understandings of the morphological characteristics of D. farinae, which is of great significance for the classification and identification.