Objective:To analyse the clinical and prognosis of C1q deposition in children with primary membranous nephropathy (PMN).Methods:A retrospective analysis was conducted in 177 children with PMN who were diagnosed by renal biopsy in the Eastern Theater Cornmand General Hospital from July 2005 to September 2013.Patients were divided into C1q deposit group and C1q non-deposit group according to the immunofluorescence staining of C1q.Clinical and pathological characteristics, treatment response, and long-term renal prognosis were compared between the 2 groups.Results:A total of 177 pediatric patients with PMN were included, involving 98 boys and 79 girls with a median age of 192.0 months.During an follow-up of (52.4±35.6) months, 7 cases(4.0%) progressed end-stage renal disease (ESRD), and 14 cases(7.9%) developed ESRD or renal dysfunction.The blood IgG level of C1q deposit group was higher than that of C1q non-deposit group [(5.10±2.51) g/L vs.(4.34±2.10) g/L, t=2.110, P=0.036]. The frequency of glomerular C4 deposits in C1q deposit group was significantly higher than that of C1q non-deposit group (34.7% vs.2.9%, χ2=32.567, P<0.001). The Kaplan-Meier survival analysis showed that there were no differences in cumulative renal survival rate of ESRD ( P=0.561) and cumulative incidence rate of remission ( P=0.291) between groups.The Logistic regression analysis demonstrated that C1q deposition was not correlated with treatment responses ( P=0.587). Univariate COX regression analysis demonstrated that the male gender ( HR=8.578, 95% CI: 1.120-65.689, P=0.039) and no remission ( HR=0.053, 95% CI: 0.017-0.171, P<0.001) were risk factors for renal dysfunction in children with PMN.Multivariate COX regression analysis reveled that no remission ( HR=21.858, 95% CI: 5.595-85.387, P<0.001) and C1q deposition ( HR=0.116, 95% CI: 0.023-0.584, P=0.009) were independent risk factors for renal dysfunction in children with PMN. Conclusions:C1q deposition was an independent risk factor for renal dysfunction in children with PMN.The classical pathway does occur in some PMN patients, which plays an essential role in mediating kidney injury.