For most of the patients with limited-stage SCLC, thoracic radiotherapy combined with chemotherapy is the standard treatment at present. However, the optimal dose / fraction of thoracic radiotherapy for limited-stage SCLC is still in controversial.This study is designed as a prospecitive randomized non-inferiority trial.

Inclusion Criteria:

1. Histologically/cytologically confirmed diagnosis of SCLC.
2. Radiologically (including brain CT/MRI, chest and abdomen contrasted CT and bone scintigraphy. PET/CT is recommended) confirmed limited-stage.
3. Patients should be between 18 and 75 years old.
4. ECOG performance status of 0-1 (Karnofsky performance status ≥ 80).
5. With adequate cardiac, pulmonary, bone marrow, hepatic and renal function.
6. With weight loss no more than 10% within 6 months before diagnosis.
7. Informed consent must be signed.

Exclusion Criteria:

1. Histology confirmed the mixed NSCLC components;
2. Other primary malignant tumors appeared within 5 years before the first administration of the study drug, except for locally curable malignant tumors after radical treatment (such as basal or squamous cell skin cancer, superficial bladder cancer or prostate, cervical or breast carcinoma in situ, etc.);
3. Any disease or condition contraindicated by radiotherapy or chemotherapy;
4. Malignant pleural effusion and pericardial effusion;
5. Pregnant and lactating women;
6. The investigator believes that the subject's complications or other circumstances may affect the compliance with the protocol or may not be suitable for the study.