Systemic lupus erythematosus (SLE) is an autoimmune disease with a loss of the control over B lymphocytes which is normally exerted by T-suppressor cell. The thymus play a central role in regulating and controlling immune reaction through its effects on T cell differentiation of both T helper and T suppressor cells. Tumors of the thymus are rare but have been reported in concurrence with a variety of autoimmune diseases, including most frequently myasthenia gravis and rarely SLE and other disorders. The association of thymoma and SLE is very rare, fewer than 10 case reports in the world literature. The woman had been thymectomized because of incidental thymoma. After two years, she was diagnosed as SLE with features of arthritis, leukopenia, high titer of ANA, positivity of anti-dsDNA and hypocomplementemia. We report here one case of concurrent SLE and thymoma.