Abstract: Objective To explore the role of synovial fluid soluble CD64 in the diagnosis of periprosthetic infection after joint replacement. Methods From December 2017 to September 2018,40 patients undergoing hip or knee revision due to joint infection or aseptic loosen admitted to our department were enrolled in our study.According to MSIS 2011 infection diagnostic criteria,20 cases were included in the periprosthetic joint infection group and 20 cases were in the non-infection group.The synovial fluid was taken by joint puncture before surgery,then the concentration of soluble CD64 in the synovial fluid was detected by ELISA,the difference between the two groups was compared,and the diagnostic efficacy of soluble CD64 in the synovial fluid for periprosthetic joint infection was analyzed by receiver operating curve. Results The mean concentration of soluble CD64 in synovial fluid in the periprosthetic joint infection group was 12.56μg/L,and it was 10.79μg/L in the non-infection group,without significant difference (P=0.288).The ROC curve of the synovial fluid soluble CD64 for predicting periprosthetic joint infection was obtained,and the area under the ROC curve (AUC) was 0.642,with 95% CI of 0.438 to 0.846 (P=0.180).The optimal cut-off value of soluble CD64 in synovial fluid was 10.145μg/L,with sensitivity of 65.2%,specificity of 63.4%,positive predictive value of 64.0%,and negative predictive value of 64.6%. Conclusion Soluble CD64 in synovial fluid has certain significance in the diagnosis of periprosthetic joint infection,but it can't be used as a preoperative screening indicator since its sensitivity is relatively low.