Endoscopic retrograde appendicitis therapy (ERAT) is a new and minimally invasive method for the diagnosis and treatment of acute appendicitis.After a positive diagnosis of acute appendicitis is established by either colonoscopic direct-vision imaging or fluoroscopic endoscopic retrograde appendicography (ERA) imaging in patients with suspected acute appendicitis, the procedures to relieve the appendiceal lumen obstruction including appendiceal luminal irrigation, appendicolith removal, and stenting for drainage whenever necessary will be carried out. In this multicenter prospective randomized clinical trial, the patients with uncomplicated acute appendicitis will be divided into three groups randomly: ERAT group, antibiotic therapy group and appendectomy group. The primary outcome is duration of abdominal pain. The secondary outcomes include mean hospital stay, mean operative time, duration of fever, duration of leukocytosis, bed time, rate of complication, rate of recurrence and rate of appendectomy during follow-up period of 1 year.