Abstract: Objective To investigate the relationship between steroid-resistant nephrotic syndrome （SRNS） and type Ⅳ collagen alpha 5 （COL4A5） gene mutation in children. Methods A total of 51 children with primary nephrotic syndrome （PNS） were enrolled. Twenty-six children who were not healed after 4-week adequate hormone therapy were assigned into the SRNS group, 25 patients who were effectively treated with adequate hormone therapy were allocated into the steroid-sensitive NS （SSNS） group, and 27 healthy children receiving physical examination were recruited as normal controls. DNA was extracted from the peripheral blood of PNS and healthy children. DNA sequencing was performed. Results COL4A5 gene mutation was detected in the PNS children rather than the normal controls. Among 51 PNS children, COL4A5 gene mutation was identified in 16 children including 8 cases of sporadic and 8 cases of genetic mutations. The COL4A5 gene mutation rate in the SRNS group was 46%, significantly higher compared with 16% in the SSNS group （P < 0.05）. The source of mutation did not significantly differ between the SRNS and SSNS children （P > 0.05）. Conclusion The COL4A5 gene mutation is closely correlated with the occurrence of PNS, which is probably associated with the steroid resistance in children.