ObjectiveTo realize direct economic cost of surgical site infection(SSI) of postthoracotomy incision. MethodsA retrospective study was conducted,1:1 match case control method was adopted to analyze direct economic cost of SSI of postthoracotomy incision in patients with SSI (case group) and without SSI (control group).  ResultsThe median of cost of hospitalization stay were 25 911.70 and 19 899.75 RMB in  case and control group respectively, the former was significantly higher than that of the latter (t=5.67, P=0.00).The median of length of  hospital stay were 32.50 and 19.50 days in case and  control group respectively,excess hospital stay were 13 days, there was significant difference between the two groups（t=10.02, P=0.00）. ConclusionSSI significantly increase medical cost and prolong length of hospital stay. Effect on infection control should be enhanced to reduce SSI rates.