Aim: To assess reliability of standardized reporting system of acute appendicitis at low-dose 320-rows CT. Methods: Retrospective analysis CT of 78 patients with pathologically proven acute appendicitis. The study was performed at low-dose 320-rows CT. The image analysis was performed by 2 radiologists according to standardized reporting system of acute appendicitis. Results: There was excellent overall of inter-observer agreement of both observers for standardized reporting system of acute appendicitis ( K = 0.89, 95% CI = 0.87-0.92, P = 0.001). There was good inter-observer agreement for visualization of appendix (K = 0.78, P = 0.001), tip diameter ( K = 0.75, P = 0.001), and single wall thickness of appendix ( K =0.77, P = 0.001). There was excellent inter-observer agreement for outer to outer wall diameter ( K = 0.82 , P = 0.001), mucosal hyper-enhancement ( K =0.80, P = 0.001), appendicolith ( K = 0.86, P = 0.001), gas in appendix ( K = 0.82, P = 0.001), surrounding fat stranding ( K = 0.81, P = 0.001), focal cecal thickening ( K = 0.85, P = 0.001), peri-appendiceal air ( K = 0.87, P = 0.001), peri-appendicular fluid collection, phlegmon, or abscess ( K = 0.82, P = 0.001), and right ovary cyst ( K = 0.83, P = 0.001). Conclusion: we concluded that excellent reliability of standardized reporting system of acute appendicitis in adults using low-dose 320-rows CT.