• Voluntarily participate in clinical research and sign written informed consent

• Male or female patients aged 18-75 years old (including the critical value)

• Histologically or cytologically confirmed SCLC

• Clinically diagnosed as IIB-IIIB ( N2) stage (AJCC 8th edition cancer staging)

• Patients who have not received systemic anti-tumor treatment or chest radiotherapy in the past

• By Surgeons evaluate patients who have no contraindications to surgery

• According to Response Evaluation Criteria in Solid Tumors (RECIST 1.1), there is at least one radiologically measurable lesion

• ECOG score 0-1

• Expected survival time \> 6 months

⁃ Hepatitis B surface antigen (HBsAg) (-) and hepatitis B core antibody (HBcAb) (-). If HBsAg (+) or HBcAb (+), the hepatitis B virus deoxyribonucleic acid (HBV-DNA) must be \<2500 copies/mL or 500 IU/mL before inclusion. Subjects who are HCV antibody (-) or HCV-RNA negative can be enrolled if HCV-RNA is positive, the subject must have alanine aminotransferase (ALT), aspartate aminotransferase (AST) ≤ Only 3×ULN can join the group. Subjects who are co-infected with hepatitis B and hepatitis C need to be excluded (positive HBsAg or HBcAb test, and positive HCV antibody test)

⁃ Laboratory tests within 7 days before the first use of the study drug confirm sufficient organ and bone marrow function, No serious hematopoietic abnormalities, cardiac, liver, renal dysfunction or immune deficiency (no blood transfusion, albumin, recombinant human thrombopoietin or colony-stimulating factor (CSF) treatment within 14 days before the first medication in this study)

⁃ Female patients must meet one of the following conditions: a. Menopause (defined as the absence of menstruation for at least 1 year without other confirmed reasons other than menopause), or b. Have undergone surgical sterilization (removal of ovaries and/or uterus) , or c. Have childbearing potential, but must meet the following requirements: the serum/urine pregnancy test within 7 days before enrollment must be negative, and agree to use contraceptive measures with an annual failure rate of \<1% or maintain abstinence (avoiding heterosexual intercourse) (from signing ICF to at least 6 months after the last dose of study drug) (contraceptive methods with annual failure rates \<1% include bilateral fallopian tube ligation, male sterilization, correct use of hormonal contraceptives that inhibit ovulation, and hormone-releasing intrauterine contraception devices and copper-containing IUDs or condoms), and you must not breastfeed.

⁃ Male patients must meet the following requirements: Agree to abstain from sex (avoid heterosexual intercourse) or take contraceptive measures, as follows: When the partner is a female of childbearing age or the partner is pregnant, the male patient must agree to abstain from sexual intercourse (avoiding heterosexual intercourse) or take contraceptive measures for at least 6 months during the study treatment period and after the last dose of the study drug. Maintain abstinence or use condoms during the first trimester to prevent embryonic drug exposure. Periodic abstinence (for example, calendar days, ovulation period, basal body temperature or post-ovulation contraceptive method) and in vitro ejaculation are unqualified contraceptive methods

⁃ The end of previous non-systemic anti-tumor treatment must be ≥ 2 weeks from the start of medication, and according to Common Terminology Criteria for Adverse Events (CTCAE) 5.0, treatment-related AEs reverted to grade ≤1 (except grade 2 alopecia).