Abstract:【Abstract】 Objective To investigate the relationship between the level of complement C3, C4, C1q and the severity of systemic lupus erythematosus (SLE) in patients with systemic lupus erythematosus (SLE). Methods From March 2017 to April 2018, 63 patients with SLE in the Department of Dermatology, Department of traditional Chinese Medicine, Department of Nephrology, and Department of Hematology of Xi'an Jiaotong University were divided into skin lesionsgroup (n=10) according to the SLE classification criteria recommended by the American Rheumatology Society in 1997. The levels of serum complement C3, C4 and C1q in newly diagnosed group (n=20), nonremission group (n=33) and healthy control group (n=45) were compared. The relationship between serum complement C3, C4 and C1q level and the active degree of systemic lupus erythematosus was analyzed. Results The levels of serum complement C3 and C4 in SLE patients were significantly lower than those in the normal control group (P<0.05). The level of serum complement C1q in SLE patients was higher than that of the normal control group (P<0.05). Conclusion The level of serum complement C3, C4 and C1q can be used to judge the degree of disease activity of systemic lupus erythematosus to some extent, and the level and variation of complement C 3, C4 and C 1q is an important indicator for the judgment of systemic lupus erythematosus of the degree of disease activity.