Objective To investigate major risk factors of mixed hemorrhoid,and provide scientific basis for primary prevention of the disease.Methods A hospital-based 1:1 matched case-control study method was adopted.A total of 341 patients who were diagnosed with mixed hemorrhoid in the Department of Anorectal Diseases,the Affiliated Hospital of Chengdu University of Traditional Chinese Medicine from June 2015 to February 2016 was recruited as case group.Another 341 non-mixed-hemorrhoid patients with the same gender proportion and age difference within 5 years old were taken as control group.Self-designed questionnaires were applied to face-to-face interview these subjects.The questionnaires included occupational factors,living habits,defecation related factors,disease history,reproductive history,family history and basic knowledge of mixed hemorrhoid.SPSS 20.0 software was used for single-factor analysis.Results It turned out that the factors related to occurrence of hemorrhoid were as followed:education level(x2 =15.431),working position(x2 =18.078),duration of single working position(OR=3.345),alcohol intake(OR=3.269),smoking(OR=1.852),spicy food intake(OR =2.409),less physical exercise(OR =1.522),defecation posture(OR =1.750),defecation time(x2 =7.516),defecation frequency(x2 =8.405),stool shape(x2 =8.004),obesity(OR=1.618),reproductive history(OR=2.211) and hemorrhoid family history of first-degree relatives(OR=1.763);The correlation intension (OR value) between anal fissure,anal pruritus and mixed hemorrhoid was 0.564 and 2.714 respectively;While tea drinking,perianal abscess or anal fistula were in no relation to mixed hemorrhoid onset.Conclusion The onset of mixed hemorrhoid is resulted from joint efforts of occupational factors,living habits,defecation habits and reproductive history,etc.Anal fissure,history of anal pruritus and preanal eczema are closely related to mixed hemorrhoid,and genetic factors may get involved as well.