Abstract: Objective To investigate the correlation of disease activity and thyroid indicators , immunologic markers of system lupus erythematosus (SLE) in SLE with Hashimoto’s thyroiditis (HT). MethodsThe clinical data of 63 cases of SLE with HT were collected. According to Systemic lupus erythematosus disease activity index 2000 (SLEDAI-2000), we classified the patients into four groups, which were remission group (5 cases), low (19 cases), moderate (12 cases) and high (27 cases) disease activity group. Each patient received the measurement of thyroid function indicators and autoantibodies, SLE immunologic indicators, serum complement (C3, C4), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and routine blood test. The correlation of thyroid indicators, immunologic markers and disease activity were analyzed. ResultsThe difference of free triiodothyronine (FT3) level in the four groups was statistically significant (P<0.05), and FT3 was negatively correlated with SLE disease activity （P=0.007）. There was no significant difference in other thyroid indicators and autoantibodies between the different groups (P>0.05). Negative correlation was found between FT3 level and anti-double-stranded DNA (dsDNA), level of anti-La antibody (SSB) and thyroid stimulating hormone (TSH) or thyroid peroxidase antibody (TPOAb). Thyroglobulin autoantibody (TgAb) was negatively related with C4, and positive correlation between FT3 and C3, FT4 and C4, TgAb and IgA. ConclusionThe pathogenesis of HT is associated with the disease activity in the patients of SLE with HT.