Systemic lupus erythematosus (SLE) is a complex autoimmune disease affecting multiple organs/systems with variable activities. We performed a retrospective study to investigate the relationship of clinical characteristics and complications with SLE activity in Chinese Han population. A cohort of 1,490 SLE inpatients was evaluated for disease activity using the systemic lupus erythematosus disease activity index (SLEDAI). Chi-square test or Fisher's exact test was used to compare differences of clinical and laboratory features between active and inactive SLE patients. Logistic regression was chosen to explore the pattern of risk factors for disease activity. We found that neuropsychiatric involvement, nephritis, arthralgia, anti-dsDNA, serositis, hypocomplementemia, oral ulcerations, erythrocyte sedimentation rate, low C3, hematological abnormalities, and systolic pressure (1.010 < odds ratio < 10.568, 1.002 < 95% confidence interval < 31.599, 0.000 < P < 0.026) were major factors associated with disease activity, but not headaches, anti-ribonucleoprotein or anti-Sm, C-reactive protein, and anemia (P > 0.05, respectively). The involvements of urinary system, respiratory system, and central nervous system were significantly more frequent in active SLE than inactive SLE (0.000 < P < 0.014), except for alimentary system (P = 0.399). Our study has comprehensively evaluated the relationship of clinical characteristics and organs/systems involvement of SLE with SLEDAI in Chinese Han population and presented a compendium of factors affecting SLE, which should be useful for better evaluating disease activity and predicting organs/systems damage in SLE for clinical assessments and managements.