Objective To investigate the relationship of ultrasonographic features with clinical severity in acute appendicitis in elderly patients in order to provide radiological references for its treatment. Methods A retrospective study was carried out on the 78 acute appendicitis patients (older than 70 years) diagnosed with clinical manifestations and auxiliary examinations in our medical center from January 2011 to January 2021. After 21 cases were excluded because of only receiving conservative and anti-inflammatory treatment, the other 57 cases were finally included, and divided into mild and severe inflammation groups based on their ultrasonogram. According to the ultrasound features, these sonographic signs were divided into direct and indirect signs. These signs were evaluated for the predictive and application values of preoperative ultrasound images for the severity of acute appendicitis in the elderly. SPSS statistics 10.0 was used for statistical analysis.Results Among the 57 cases, pathological observation confirmed that 33 cases were in mild inflammation group, and 24 cases were in severe inflammatory group. The diagnosis coincidence rate of mild inflammation and severe inflammation group were 78.79% (26/33) and 83.33% (20/24), respectively. In the mild inflammatory group, the main sonographic features were direct signs, such as widened appendix diameter, tubular hypoechoic, weak peristalsis or no peristalsis. In contrast, indirect signs such as widened cecum, omental adhesion or wrapping, abscess formation, and intestinal effusion were more common in the severe inflammation group, but there were few direct signs. The direct and indirect signs were highly consistent with the intraoperative findings. Conclusion Ultrasonographic features can provide radiological indicators in evaluation of the severity of acute appendicitis in the old patients. These features show guidance value for clinical therapy, and also might be used as a reference for surgical timing.