It can be diagnosed according to the clinical manifestations of redness, swelling, heat and pain around the anus, combined with the results of laboratory tests and imaging examinations, and differentiated from actinomycosis and tuberculous abscess. 1. Physical examination (1) Visual examination: observe the local pus and skin condition. The pus is thick, yellowish in color and large in quantity, mostly due to acute inflammation caused by Staphylococcus aureus. Mixed with green pus, should be considered Pseudomonas aeruginosa infection; thick yellow color and smell, mostly belong to Escherichia coli infection; pus is clear and thin rice-like, mostly belong to Mycobacterium tuberculosis infection. (2) Fingerprinting: fingerprinting is important to understand the morphology and nature of abscess, the presence of fistulas, fistulas, and the level of muscle involvement. 2.Laboratory examination (1) blood routine: white blood cell count can reflect the degree of systemic infection. (2) pus bacterial culture: to determine the causative bacteria, to guide the treatment of drugs. 3. Imaging examination: rectal cavity ultrasonography can accurately diagnose perianal abscess, especially for the diagnosis of high abscess which is difficult to be diagnosed by usual methods. Nuclear magnetic resonance (MRI) has the advantages of accuracy not lower than that of rectal cavity ultrasound and painlessness, but the cost is high. 4. Other examinations: probe examination and methylene blue examination are used to determine the location of the inner mouth. Endoscopy can observe the rectum with or without endostomia, pus and blood and other lesions. It is recommended to consult the hospital in time.