The purpose of this study is to initially access the safety and effectivity of RC18 combined with standard treatment and Placebo combined with standard therapy in subjects with Moderate to severe SLE, Besides ,to provide dose basis for follow-up clinical trials.

Inclusion Criteria:

• Active SLE disease，and at least according with 4 of the 11 items of the American College of Rheumatology (ACR) criteria 1997.
• Age & Gender: Male or female between 18 and 65 years of age inclusive，and the sex ratio is not limited
• Signed informed consent form，willing or able to participate in all required study evaluations and procedures.
• SELENA-SLEDAI(Safety of Estrogens in Lupus Erythematosus National Assessment SLE Disease Activity Index) score ≥ 8 during the screening period.and if there is hypocomlement or the Anti-dsDNA score, SELENA-SLEDAI disease activity score should be at least 6 at screening .
• Autoantibody-positive
• on a stable SLE treatment regimen for at least 30 days prior to Day 1, which consisted of any of the following (alone or in combination): cortical hormone,anti-malarials,non-steroidal anti inflammatory drugs (NSAIDs),or any immunosuppressive and immunomodulator therapy(i.e.,azathioprine,mycophenolate ,cyclophosphamide,methotrexate,leflunomide, Tacrolimus ,ciclosporin ).

Exclusion Criteria:

• Severe lupus nephritis within two months(designed as:Urine protein>6g/24h or serum creatinine ( SCr）>2.5mg/dL or 221umol/L ) or needing for hemodialysis or recepting high dose cortical hormone ≥14 days( metacortandracin>100mg/d or equivalent)
• Central nervous system disease caused by SLE or non SLE within two months (including epilepsy， mental disease，organic encephalopathy syndrome，cerebrovascular accident, encephalitis, central nervous system vasculitis）;
• there are serious heart, liver, kidney and other important organs and blood, endocrine system diseases and medical history;

Evaluation criteria for severity :

1. Alanine aminotransferase（ALT）or aspartate aminotransferase (AST) ≥2 upper limit of normal (ULN);

2. Creatinine Clearance (Ccr)<30ml/min;

3. White Blood Cell Count(WBCs)<2.5x 10(9)/L;

4. hemoglobin<85g/L;

5. Platelets<50x 10(9)/L.

   • Have a historically active hepatitis or active hepatitis or medical history,hepatitis B :Patients with positive HBsAg are excluded.;Hepatitis C: Patients with hepatitis C antibody positive are excluded;
   • Immune deficiency, uncontrolled severe infection and patients with active or recurrent peptic ulcer;
   • Pregnant , lactating women and men or women who have birth plans in the past 12 months ;
   • Have a history of allergic reaction to human biological medicines.
   • Receipt of live vaccine within 1 month;
   • Have participated in any clinical trial in the first 28 days of the initial screening or 5 times half-life period of the study compound (taking the time for the elderly).
   • Have received treatment with B cell targeted therapy such as Rituximab or Epratuzumab etc.
   • Receipt of anti-tumor necrosis factor、interleukin receptor antagonist；
   • Receipt of IV immunoglobulin（IVIG）,prednisone>100mg/d more than 14 days or plasma exchange;
   • There are active infections (such as herpes zoster, human immunodeficiency virus (HIV) virus infection, active tuberculosis, etc.) during the screening period;
   • Patients have depression or the significant suicide ideation;
   • Investigator considers candidates not appropriating for the study.