Background: It has been reported that donor derived cell-free DNA(dd-cfDNA) accounts for less than 1.2% of total cell free DNA in stable kidney allograft recipients, and dd-cfDNA may be a non-invasive biomarker of acute rejection. However, the kinetics of plasma dd-cfDNA level is still unclear, which hinders the further application of dd-cfDNA in kidney transplantation (KTx). The purpose of this study was to explore the correlation between plasma dd-cfDNA and delayed graft function(DGF） and pulmonary infection after KTx, and to explore the diagnostic value of dd-cfDNA in DGF. In addition, we tried to find out the factors related to the rebound of dd-cfDNA level.Methods: A total of 183 kidney transplant recipients were enrolled in this study. Peripheral blood samples (10ml) were collected on the 1st, 7th, 14th and 21st day after KTx, and 546 plasma samples were collected. Droplet digital PCR (DDPCR) was used to detect the level of dd-cfDNA(%) and Mann Whitney U test was used to analyze the relationship between dd-cfDNA level and DGF and pulmonary infection. Logistic binary regression analysis was used to analyze the clinical factors related to the increase of dd-cfDNA.Results: There was no significant difference between DGF group and non-DGF group of dd-cfDNA level (P > 0.05). The mean value of dd-cfDNA on day 1 (6.97%) was significantly higher than that on day 7 (1.17%), day 14 (1.09%) and day 21 (1.18%). Logistic binary regression analysis was performed for dd-cfDNA level rebound group and non-rebound group. Pulmonary infection (OR = 2.11, P = 0.028) and DGF (OR = 1.37, P = 0.42) were significantly correlated with rebound of dd-cfDNA. At the same time, on the 1st, 7th and 14th day after KTx, the levels of dd-cfDNA in pulmonary infection group was significantly higher than non-infection group (P < 0.05).Conclusion: Our results indicate that dd-cfDNA (%) can’t be used as a biomarker for predicting DGF. The rebound of plasma dd-cfDNA (%) level was significantly correlated with the presence of pulmonary infection. However, further confirmatory studies are necessary.