Objective To present the concept and explore the diagnosis and treatment strategies of secondary appendicitis. To summarize the clinical features of secondary appendicitis caused by different related factors. Methods The clinical data of 660 patients with a presumptive diagnosis of acute appendicitis between November 2003 and November 2008 in The First Affiliated Hospital of Harbin Medical University were collected and analyzed retrospectively. Five hundred and ninetyfour patients with primary appendicitis (primary appendicitis group), and 66 patients with secondary appendicitis (secondary appendicitis group). Clinical parameters such as fever， nausea or vomit, abdominal pain, abdominal distension, change of defecation habits or characters, tenderness in the right lower abdominal quadrant, acute abdomen, abdominal mass, and WBC were compared between two groups. Results Biopsies of appendectomy were taken in all and the results showed inflammation. The pathogenic factors and cases of primary appendicitis: bacterial infection in 171 cases (25.91%), appendix cavity blocked by fecalith in 386 cases (58.48%), appendix cavity stricture in 33 cases (5.00%), and appendix deformity in 4 cases (0.61%). Sixty-six patients resulted from secondary appendicitis: colon carcinoma in 7 cases (1.06%) receiving laparocolectomy including 5 ascending colon and 2 transverse colon; gynecological disease in 20 cases (3.03%), 7 cases of right ovarian cyst accompanying adnexal torsion receiving oophorocystectomy combining with appendectomy, 5 right rupture of corpus luteum of ovary receiving right ovariectomy combining with appendectomy, 4 acute pelvic inflammation and pelvic abscess receiving transvaginal drainage of pelvic abscess combining with appendectomy, 4 extra-uterine pregnancy receiving right ovariectomy and salpingectomy combining with appendectomy; 9 cases (1.36%) of hernia, all to be right oblique hernia, receiving herniorrhaphy combining with appendectomy; Intestinal tuberculosis in 6 cases (0.91%), 4 cases receiving appendectomy, 1 case for resection of ileocecum, and 1 case for right hemicolectomy; parasitic disease in 24 cases (3.64%), all to receive appendectomy. There were significant differences in nausea or vomit, abdominal pain, abdominal distension, changes of defecation habit or character, tenderness in the right lower abdominal quadrant, abdominal mass, and WBC between two groups (Plt;0.05). There was no significant difference in fever or acute abdomen between two groups (Pgt;0.05). InclusionsAppendicitis could be secondary to many diseases. We must attach importance to the diagnosis of secondary appendicitis so that to decrease or avoid the appearance of missed diagnosis and misdiagnosed in the clinical.