Objectives To analyze risk factors associated with conversion to open surgery of laparoscopic repair for perforated peptic ulcer. Methods From January 2009 to December 2014, 235 patients underwent laparoscopic repair for perforated peptic ulcer in the Chengdu 5th Hospital, were enrolled in this study. These patients were divided into laparoscopic repair group (n=207) and conversion to open surgery group (n=28). The characteristics, clinical outcomes, and prognosis factors were compared between these two groups. The receiver operating characteristic (ROC) curve was used to determine the critical cutoff value for diameter and duration of perforation for predicting conversion to open surgery. Results There were no significant differences of the age, gender, body mass index, comorbidity, history of ulcer, smoking history, history of nonsteroidal antiinflammatory drugs or steroids use, history of alcohol use, American Society of Anesthesiologists classification on admission, white blood cell count on admission, C reaction protein on admission, surgeons, suture method, and location of perforation between these two groups (P>0.05). The patients in the conversion to open surgery group had a higher procalcitonin (PCT) level on admission (P=0.040), longer duration of peroration (P<0.001), larger diameter of peroration (P<0.001), longer hospital stay (P=0.002), higher proportion of patients with Clavien-Dindo classification Ⅰ and Ⅱ (P<0.001), longer gastrointestinal function recovery time (P=0.003), longer analgesics use time (P<0.001), and longer off-bed time (P=0.001) as compared with the laparoscopic repair group. The results of logistic regression analysis showed that the peroration duration on admission〔OR: 2.104, 95%CI (1.124, 3.012),P=0.020〕and peroration diameter on admission〔OR: 2.475, 95%CI (1.341, 6.396),P=0.013〕were two predictors of conversion to open surgery. For the diameter of perforation, 8.0 mm was the critical cutoff value for predicting conversion to open surgery by ROC curve analysis, the sensitivity was 76%, the specificity was 93%, and the area under the curve (AUC) was 0.912. For the duration of perforation, 14 h was the critical cutoff value to predict conversion to open surgery, the sensitivity was 86%, the specificity was 71%, and theAUC was 0.909. Conclusions The preliminary results in this study show that diameter of perforation of 8 mm and duration of perforation of 14 h are two reliable risk factors associated with conversion to open surgery for perforated peptic ulcer. Also, PCT level would mightbe considered as a helpful risk factor for it.