Abstract: Objective To investigate the pathology of acute incarcerated and mixed hemorrhoid （AIIH）. Methods Samples were collected from 48 patients with acute incarcerated hemorrhoid and from 52 patients with mixed hemorrhoid at hemorrhoidectomy from January 2007 to May 2008. Rectal mucosa and tissue were stained with hematoxylin and eosin （H＆E） and compared. Results Hanges were observed in blood vessels, connective tissue, muscular and interstitial tissue and rectal mucosa of incarcerated hemorrhoid with infiltration of chronic inflammatory cells. However, no statistical difference was found in the number, types and depth of inflammatory cell infiltration between acute incarcerated and mixed hemorrhoids（P＞0.05）. Conclusion Incarcerated hemorrhoid is the severe stage of hemorrhoid pathology with no infection at its early stage. Its pathologic changes are similar to those of mixed hemorrhoid.