Objective To explore the advantage of motor evoked potentials (MEPs) monitoring for postoperative motor deficit evaluation under threshold-level electrical stimulation using cranial peg-screw electrode (CPSE) during cerebral aneurysm keyhole approach microsurgery. Methods A total of 31 patients who underwent anterior circulation aneurysm microsurgery through keyhole approach were selected in this study. MEPs monitoring of the operation side was conducted with threshold-level electrical stimulation using CPSE, and that of the non-operation side was conducted with transcranial electric stimulation using the same stimulation threshold. The change of minimum voltage required for MEPs monitoring was observed and recorded. The intraoperative MEPs monitoring results and postoperative neurological functions were analyzed by prospective observational study. Results MEPs of the operation side was successfully induced in 28 cases. No complications related to MEPs monitoring were observed. Intraoperative MEPs abnormalities were monitored in 3 cases, and 2 of them had postoperative transient hemiplegia, showing a sensitivity of 100% (2/2). No motor dysfunction was observed in the other 26 cases who were not presented with intraoperative MEPs abnormalities in 25 cases, showing a specificity of 96.30%(26/27). Conclusion MEPs monitoring with threshold-level electrical stimulation using CPSE is a feasible and reliable method and it has satisfactory sensitivity and specificity for predicting motor dysfunction induced by cerebral ischemia, indicating that this method can be an alternative for routine MEPs monitoring with conventional transcranial electrical stimulation in cerebral aneurysm microsurgery.