Unplanned reoperation is a key indicator in surgical care category of Taiwan Clinical Performance Indicator and is highly correlated with complications associated with the previous operation. Distinguishing between planned and unplanned and related and unrelated surgery is difficult, and the correctness of indicators is frequently disputed. The research team used project management techniques (1) to obtain consistent and correct indicator statistics; (2) to analyze the reasons for unplanned reoperation; and (3) to improve surgical safety and care quality. Compared with 2014, in 2015, the incidence of unplanned reoperation (P value) in Ditmanson Medical Foundation Chia- Yi Christian Hospital decreased from 1.2% to 0.67% and further decreased to 0.61% in 2017 and 2018. Through the case-by-case analysis of cases presented at the surgical quality conference, the consensus on medical, nursing, and computer statistics was integrated to enhance data accuracy. Through reexamination of the definition of critical indicators, the process of indicator acceptance, and the source of values using project management techniques, an internal audit system for indicators and a mechanism for the self-verification of the correctness of indicator data was established to strengthen the attention and participation of medical personnel in medical quality, thereby improving medical quality and patient safety.