Objective: The aim of this study is to determine the role of urinary alpha 1 acid glycoprotein is a biomarker in the renal disease activity in systemic lupus erythematosus (SLE). Methods: eighty patients were divided into 4 groups: G1 active renal SLE (LN- A) (n=40), G2 inactive renal SLE patients (LN- R) (n=20), G3 SLE patients without renal disease but with other extrarenal involvement (NR-SLE) (n=20) and G4 normal control subjects (n=40). All patients were subjected to full history taking, full examination, urinary (AGP) measured in patients and controls and repeated after 3 months in patients and controls and all the laboratory and radiological examination needed for SLE diagnosis are done. Disease activity indices in form of SLEDAI-2K and its renal parameter and BILAG and its renal parameter and SDI-R were evaluated to all SLE patients. Results: Mean concentrations of basal urinary AGP is higher in SLE patients with active renal disease than SLE patients with inactive renal disease and SLE patients without renal disease but with other extrarenal involvement and control with significant statistical difference. There were significant correlation in group 1 between uAGP with (SLEDAI-2K),(SLEDAI-R),(BILAG -R), (SDI -R), creatinine, urea, RBCs in urine, casturia, pyuria, urinary protein creatinine ratio, GFR, Anti ds- DNA, C3 ,C4, BAI score and BCI Score, ESR, Age at diagnosis, current age and disease duration. Multiple linear regression analysis shows that BILAG-R score, ESR, Pyuria, RBCs in urine, C3, C4, Capillary proliferation finding on renal biopsy and BCI Score are significant predictors for active group of lupus nephritis. Logistic regression analysis of urinary AGP show that BILAG -R score is reliable predictor for renal damage in SLE patients. Both (AUC which is 0.957 and cutoff value of urinary AGP which is 756) achieved Sensitivity is 95%, specificity is 27.5%, positive predictive value is 88.37%, negative predictive value is 94.59% and accuracy is 91.25%. Mean AGP levels at follow-up after three months of therapy showed significant statistical difference (p value 0.000) in patients having CR/PR.so early diagnosis of LN by using urinary AGP help in early treatment. Conclusion: Urinary alpha 1 acid glycoprotein could be used as a biomarker of activity and severity of lupus nephritis.