• 18 years old ≤ 75 years old; Both male and female;

• ECOG 0-1;

• Histologically or cytologically confirmed non-small cell lung cancer;

• Progression with brain metastasis after previous first-line anti-tumor therapy;

• Requirements for brain metastases: ① measurable brain metastases without radiotherapy; ②SRS/FSRT: the maximum tumor volume of brain metastases was less than 10cm3, the single diameter was less than 3cm, and the total volume of brain metastases involved was less than 15 cm3.

• Response to previous checkpoint inhibitor therapy on the initial response assessment;

• If a metastatic lesion of the head has been irradiated, the cumulative radiation dose does not exceed the tolerated dose to all structures.

• For patients with measurable CNS lesions, the longest diameter on MRI images is ≥10mm, which is suitable for repeated and accurate measurement.

• Subjects were evaluated for all extracranial disease sites (e.g., by computed tomography (CT) scan and bone scan or positron emission tomography (PET-CT) within 14 days before the first dose.

⁃ Subjects had to have a baseline brain MRI scan within 14 days before the first dose of medication.

⁃ Estimated survival time \> 12 weeks.

⁃ Participants of childbearing age must agree to use effective contraception during the trial; In women of childbearing age, a serum or urine pregnancy test must be negative.

⁃ Patients who are not lactating.

⁃ Have definite and good organ functions:

⁃ Provide informed consent voluntarily, and be willing and able to comply with the follow-up, treatment, laboratory testing, and other study requirements specified in the study schedule.