Abstract: Objective To explore the correlation between serum level of complement C3 and abdominal aortic calcification(AAC) in maintenance hemodialysis(MHD) patients.Methods A total of 127 MHD patients hospitalized between February 2019 and December 2019 were selected.Based upon to the points of AACs,they were divided into the groups of non-calcification(AACs<1,n=31),mild calcification(1 ≤ AACs<5,n=36),moderate calcification(5 ≤ AACs ≤ 15,n=32) and severe calcification(AACs>15,n=28).The relevant clinical data were collected and serum level of complement C3 was detected.The difference of serum complement C3 level with different degree of calcification and its correlation with AAC were analyzed.The influencing factors of AAC were analyzed by Logistic regression.The predictive value of serum level of complement C3 for AAC was analyzed by plotting the curve of receiver operating characteristic(ROC).Results The levels of serum phosphorus,intact parathyroid hormone(iPTH) and complement C3 were significantly higher in mild/moderate/severe calcification group than those in non-calcification group(P<0.05);levels of serum phosphorus,iPTH and complement C3 significantly higher in moderate/severe calcification group than those in mild calcification group(P<0.05);the levels of serum phosphorus,iPTH and complement C3 significantly higher in severe calcification group than those in moderate calcification group(P<0.05).Serum level of complement C3 was positively correlated with serum phosphorus,iPTH and AACs points(P<0.05).And serum levels of phosphorus,iPTH and complement C3 were independent risk factors of AAC(P<0.05).And the area under curve(AUC) of serum complement C3 was 0.858 for predicting AAC(P<0.05).Conclusion Serum level of complement C3 is associated with the severity of AAC.As one of the independent risk factors for AAC,it may become an important biological marker for predicting the occurrence of AAC in MHD patients.