Objective To investigate the efficacy and dosimetric characteristics of different radiotherapy modalities in the elderly patients with multiple brain metastases from non-small-cell lung cancer with a view to providing a basis for clinical decision on radiotherapy modalities for such patients. Methods A total of 115 elderly patients with multiple brain metastases from non-small-cell lung cancer admitted to Qingdao Central Hospital Affiliated to Qingdao University from August 2018 to August 2021 were retrospectively analyzed. According to the radiotherapy modalities employed, they were divided into whole-brain radiotherapy group (n=40), sequential boost group (n=33), and simultaneous integrated boost group (n=42). SPSS 26.0 was used for statistical analysis. Analysis of variance, t test or Chi-square test was used for inter-group comparison depending on the data type. Results The effective rate was 47.5% (19/40) in the whole-brain radiotherapy group, 60.6% (20/33) in the sequential boost group, and 76.2% (32/42) in the simultaneous integrated boost group. The local control rates were 72.5% (29/40), 87.9% (29/33) and 95.2% (40/42), respectively. The effective rate and disease control rate in the simultaneous integrated boost group were higher than those in the whole-brain radiotherapy group, and the differences were statistically significant (P<0.05). The one-year intracranial progression-free survival (IPFS) rates were 25.0% (10/40), 69.7% (23/33) and 73.8% (31/42), and the one-year overall survival (OS) rates were 47.5% (19/40), 75.8% (25/33) and 78.6% (33/42) in the whole-brain radiotherapy group, sequential boost group, and simultaneous integrated boost group, respectively. The IPFS rate and OS rate at 1 year were higher in the sequential boost group and simultaneous integrated boost group than those in the whole-brain radiotherapy group, and the differences were statistically significant (P<0.01). Conformation number (CN) and prescription isodose volume to target volume ratio (PITV)(0.88±0.04,1.06±0.06) of planning tumor volume (PTV) in the simultaneous integrated boost group were better than those in the whole-brain radiotherapy group (0.86±0.07,1.11±0.13), which were better than those in the sequential boost group (0.81±0.05,1.21±0.08), and the differences were statistically significant (P<0.01). Target coverage (TC) of PTV in the sequential boost group (0.99±0.01) was better than that in the whole-brain radiotherapy group (0.97±0.17) and that in the simultaneous integrated boost group(0.97±0.02), and the difference was statistically significant (P<0.05). Homogeneity index (HI) of PTV in the whole-brain radiotherapy group (0.06±0.02) was better than that in the simultaneous integrated boost group (0.25±0.07), which was better than that in the sequential boost group (0.36±0.12), and the differences were statistically significant (P<0.01). CN and PITV of plan gross tumor volume in the simultaneous integrated boost group (0.79±0.10,1.25±0.21) were better than those in the sequential boost group (0.67±0.13,1.54±0.45), and the diffe-rences were statistically significant (P<0.01). Number grade 3 or higher adverse reactions occurred in any of the three groups. Conclusion The whole brain radiotherapy combined with simultaneous integrated boost can be the optimal treatment for the elderly patients with multiple brain metastases from non-small-cell lung cancer.