Objective: To assess the association between lupus nephritis disease activity and anti-C1q antibodies. Methods: The study analyzed the medical records of 98 patients with lupus nephritis (LN), 35 patients without lupus nephritis. LN disease activity was measured by the systemic lupus international collaborating clinics (SLICC) renal activity score of 2008. All biopsied tissues were scored based on the International society of nephrology/Renal pathology society (ISN/RPS) 2003 LN pathological typing standards, acute and chronic index scores were used to evaluate the activities of lupus. All patients were test for the levels of anti-dsDNA and anti-C1q antibodies using the enzyme-linked immuno sorbent assay (ELISA), C3, C4, 24-hour urinary protein performed in parallel. For normally distributed quantitative parameters, the differences between groups were assessed by t test. Mann-Whitney U test was performed for non-normally distributed data. The cut-off values were evaluated by using receiver operating characteristic (ROC). The Spearman methods were used to test correlations. Results: Patients with LN had a higher levels of anti-C1q antibodies than patients without lupus nephritis [3.94 (10.2, 91.3) AU/ml与6.9 (2.0, 15.4) AU/ml; Z=-4.299, P<0.01]. Patients with inactive lupus nephritis had higher levels of C1q, C3, C4 than active LN (t=2.393, 3.777, 2.557; P<0.05). Patients with active lupus nephritis had higher levels of anti-C1q antibodies than inactive LN (Z=-4.632, P<0.01). Anti-C1q antibody levels were positively correlated with levels of 24-hour urinary protein, AI score (r=0.327, P<0.01) and SLICC score (r=0.493, P<0.01), and were negatively correlated with serum C1q (r=-0.373, P<0.01), C3 (r=-0.532, P<0.01) and C4 (r=-0.463, P<0.01). The optimal cutoff value of Anti-C1q for a diagnosis of active LN was 48.9 RU/ml, and the sensitivity and specificity were 62.5% and 80%, respectively. The area under the curve (AUC) was 0.771. Conclusion Anti-C1q antibodies are more closely correlated with renal disease activity, and anti-C1q antibody is an important serum marker for monitoring LN activity, but its pathological mechanism in the pathogenesis of LN still needs to be further explored.