This study aimed to explore the neural mechanism underlying high-altitude (HA) adaptation and deadaptation on perceptual processes in lowlanders. Eighteen healthy lowlanders were administered a facial S1-S2 matching task that included incomplete face (S1) and complete face (S2) photographs, combined with ERP technology. Participants were tested shortly before they went to HA at sea level (Test 1), twenty-five days after entering HA (Test 2), one week (Test 3) and one month (Test 4) after returning to lowlands. Compared with sea level baseline, shorter latencies of P1 and N170 and larger amplitudes of complete face N170 were found in HA. After returning to sea level, compared with HA, the amplitude of the incomplete face P1 was smaller after one week and the complete face was smaller after one month. The right hemisphere N170 amplitude was larger after entering HA and one week after returning to sea level compared to baseline, but it returned to baseline after one month. Taken together, the current findings suggest that HA adaptation increases visual cortex excitation to accelerate perceptual processing. More mental resources are recruited during the configural encoding stage of complete faces after HA exposure. The perceptual processes affected by HA exposure is reversible after returning to sea level, but the low-level processing stage is different between incomplete and complete faces due to neural compensation mechanisms. The configural encoding stage in the right hemisphere is affected by HA exposure and requires more than one week but less than one month to recover to baseline