Objective? To evaluate the effect and value of CT scan in preoperative diagnosis of acute appendicitis.Methods From November 2018 to September 2020，60 patients with acute appendicitis were selected from Jinxi People's Hospital of Kunshan City. They were examined by B-ultrasound and CT scan before operation. The results of B-ultrasound and CT scan were compared and compared with those of pathology. The diagnosis results and specific scanning characteristics were analyzed. Results? Acute appendicitis patients with CT and B-ultrasound scanning，the pathological types can be divided into simple，suppurative，gangrenous perforating type and periappendiceal abscess. The positive rate of simple CT scanning was significantly higher than that of B-ultrasound，and the difference was statistically significant（P＜0.05）. Taking surgical pathological results as the gold standard，the diagnostic accuracy rate of CT scanning in 60 patients was 93.33%，significantly higher than that of B-ultrasound 58.33% The difference was statistically significant（P＜0.05）. Conclusion? The diagnostic results of multi-slice spiral CT scanning are similar to those of surgical pathology. The accuracy of scanning results is high，which provides valuable basis for clinical further quality.