Objective：To explore the correlation between magnetic resonance（MR）findings[optic nerve sheath diameter（ONSD） and peripheral cerebrospinal fluid volume/intracranial volume ratio（PCSFV/ICV）]and cerebrospinal fluid pressure（CSFP）in patients with leptomeningeal metastases（LM）from non - small cell lung cancer（NSCLC）. And to assess the diagnostic accuracy of combined ONSD and PCSFV/ICV in diagnosing elevated CSFP. Methods：A total of 63 patients with NSCLC-LM were enrolled. Both optic nerve and cranial MR scans were performed to measure bilateral ONSD，cranial PCSFV and ICV. Subsequently，CSFP was measured in all patients through lumbar puncture，and intrathecal chemotherapy was administered regularly. Pearson correlation analysis was used to analyze the correlation between CSFP and MR findings. The accuracy of combined ONSD and PCSFV/ICV in diagnosing elevated CSFP was evaluated through receiver operating characteristic（ROC）curve analysis. Results：In patients with NSCLC-LM，the average ONSD of bilateral eyes was positively correlated with CSFP（r=0.567，P ＜ 0.001）. PCSFV/ICV was negatively correlated with CSFP （r=-0.365，P=0.003）. ROC curve analysis showed that the performance of ONSD，PCSFV/ICV，and combined ONSD with PCSFV/ICV in diagnosing intracranial hypertension（CSFP＞15 mmHg）were 0.81（95%CI：0.71-0.91），0.76（95%CI：0.64-0.89），and 0.91（95%CI：0.84-0.99），respectively. The performance of ONSD，PCSFV/ICV，and combined ONSD with PCSFV/ICV in diagnosing intracranial hypertension（CSFP＞20 mmHg）were 0.70（95%CI：0.58-0.82），0.72（95%CI：0.57-0.88），and 0.81（95%CI：0.70-0.93），respectively. Conclusion：The utilization of MR for measuring ONSD and PCSFV/ICV provides a valuable means to assess variations in CSFP among patients diagnosed with NSCLC -LM. Additionally，the combination of these two measurements enhances the diagnostic accuracy for evaluating CSFP，demonstrating its potential clinical significance.