Objective: To explore whether streptococcal infection may aggravate renal damage in children with Henoch-Schönlein purpura nephritis and its possible mechanism. Methods: In the study, 485 children diagnosed with Henoch-Schönlein purpura nephritis from July 2015 to December 2019 were selected to analyze their clinical data retrospectively. According to the diagnosis of discharge, whether it was combined with streptococcal infection, the children were divided into two groups. The experimental group contained 91 children with Henoch-Schönlein purpura nephritis combined with streptococcal infection, and there were 394 children who were not infected with Streptococcus in the control group. Suitable test items were preliminarily selected through artificial neural network, and then data analysis was performed through SPSS 23.0. Results: The children with Henoch-Schönlein purpura nephritis infected with streptococcus had statistically significant differences compared with the uninfected children in the test items of urine protein, liver and kidney function, immunoglobulin and complement. Anti-streptolysin O had mild correlation with IgG (Spearman r=-0.328), fibrin degradation products (Spearman r=-0.207), total protein (Spearman r=-0.202) and globulin (Spearman r=-0.223). Compared with the children who were not infected with streptococcus, the differences of the average levels of age (P=0.001), IgG (P < 0.001), fibrin degradation products (P=0.019), total protein (P < 0.001), globulin (P < 0.001), IgA (P < 0.001), IgM (P=0.003), complement 3 (P=0.016), complement 4 (P=0.002), albumin/globulin ratio (P=0.007), alkaline phosphatase (P=0.036), and estimated glomerular filtration rate (P=0.039) in the infected children were statistically significant. In order to explore the risk factors of kidney damage in the children with Henoch-Schönlein purpura nephritis, Logistic regression was performed using anti-streptolysin O, age, immunoglobulin and complement as independent variables, urine protein detection parameters, liver and kidney functions as dependent variables. Age ≤10 years old and hypocomplementemia might be risk factors for aggravating renal damage in the children with Henoch-Schönlein purpura nephritis. Conclusion: Streptococcal infections may aggravate renal damage in children with Henoch-Schönlein purpura nephritis, in which hypocomplementemia, inflammation, fibrinolysis and disorders of coagulation perhaps play an important role. Children with streptococcal infection should be treated with anti-infective treatment in time and necessarily, and followed up after discharge regularly.