Purpose: The purpose of this study was to investigate the current humidification state of incubator, the factors disturbing high humidification and to establish the evidence-based nursing protocol to maintain it. Methods: The subjects were 15 infants who were born with extremely low birth weight (ELBW) from May to October, 2007, and data were collected during the first 3 days and analyzed with SPSS WIN program. Results: The goal of humidity level in incubator was 95%, but mean humidity levels were 89.7%(1st day), 91.9%(2nd day), and 91.8%(3rd day)(p<0.001). The disturbing factors were opening frequency and duration of incubator door and window by caregivers. The handling of infants by nurses and doctors happened more frequently during the first day. Especially, nurses handled them more often than others, but the duration of opening during the invasive procedures by doctors was longer than others. The opening frequency had negative correlation with duration(r=-.779, p<.01). Conclusion: So the evidence-based protocol for maintaining high humidity in incubator for ELBW infants during the first 3 days and next 2 days was made. Furthermore we need to educate NICU nurses and doctors about minimal handling.