Our objective was to explore the best predictive timing of short-latency somatosensory evoked potentials (SLSEP) and brainstem auditory evoked potentials (BAEP) for unfavorable outcomes in patients with early stage severe stroke. One hundred fifty-six patients with acute severe supratentorial stroke were monitored according to SLSEP, BAEP, and the Glasgow Coma Scale (GCS) at 1-3 days and 4-7 days after the onset of stroke. All patients were followed up for outcomes at 6 months after onset using the modified Rankin Scale (mRS), with a score of 5-6 considered unfavorable. The predictive values of SLSEP, BAEP, and the GCS at 1-3 days were compared with 4-7 days after onset. Our results show that, according to the analysis of prognostic authenticity, the predictive values of SLSEP and BAEP at 4-7 days after stroke onset improved when compared with the values at 1-3 days for unfavorable outcomes. Most of the patients with change of worsening evoked potentials from 1-3 days to 4-7 days after onset had unfavorable outcomes. In conclusion, SLSEP and BAEP assessed at 4-7 days after onset predicted unfavorable outcomes for acute severe stroke patients. The worsening values of SLSEP and BAEP between 1-3 days and 4-7 days also present a prognostic value.