Objective Treatment and histopathological observation of demodex canis in beagle dogs. Methods Using the method of direct smear for microscopic examination of demodex canis. Histopathological observation on the skin of the parasitic parts after routine paraffin section and HE staining. Results (1) Clinical observation:The red spots and hair removal was appeared on limbs, eyes, lower abdomen and other parts of the skin of canine patients.The skin of the limbs becomes thicker and wrinkles. (2) Blood routine examination:Basically normal. (3) Microscope observation:The results showed that a large number of worms and eggs of small demodex canis could be found. (4) Histopathological observation:Hair follicles showed a large number of demodex mites and eggs. The sebaceous glands and sweat glands have normal morphology and no mites was found. A large number of eosinophils and neutrophil infiltration were seen around the hair follicles. It was also found that the formation of multifocal granuloma:the granuloma was oval shaped. (5) Treatment programme:The combination of medication and the strengthening of environmental control has been shown to be effective. Conclusions Granuloma caused by demodex canis can be divided into immune granuloma.It may not be possible to destroy the sebaceous glands after infection with small demodex canis.Whether the sebaceous gland is infected with the demodex canis may be associated with the worm species or course of disease.