Objective: To investigate the diagnostic value of interleukin 6 (IL-6) and serum amyloid protein A (SAA) in relapse of primary nephrotic syndrome combined with infection in children. Methods: 78 children with relapse of primary nephrotic syndrome were divided into 3 groups: group A, 42 children with relapse of primary nephrotic syndrome combined bacterial infection; group B, 24 children with relapse of primary nephrotic syndrome combined viral infection; group C,12 children with relapse of primary nephrotic syndrome with non infection. The serum IL-6 level and SAA of children in 3 groups were respectively detected, and ROC curve were established to evaluate the diagnostic value of IL-6 and SAA in relapse of primary nephrotic syndrome combined with bacterial infection. Results: The positive rate of IL-6 and SAA (85.71%, 71.43%) of children in group A were significantly higher than group B (0.00%, 20.83%) and group C (16.67%, 33.33%, P<0.05). The AUC of IL-6 and SAA was respectively 0.899 and 0.56. When the cutoff point of IL-6 was 10.71, the sensitivity, specificity, Youden index, positive likelihood ratio and negative likelihood ratio of IL-6 in diagnosing primary nephrotic syndrome combined with bacterial infection were 85.7%, 91.7%, 0.774, 10.33 and 0.16. Conclusions: Detection of SAA and IL-6 can be used to distinguish primary nephrotic syndrome combined bacterial infection from with viral infection and non infection. Moreover, IL-6 has a higher diagnostic value in primary nephrotic syndrome combined with bacterial infection.