Abstract: Dongting Lake is a very important habitat for the wintering tundra swan (Cygnus columbianus). The wintering behavior of adult and juvenile tundra swan population was investigated by an instantaneous scanning sampling method. The results showed that adult and juvenile tundra swan had roughly the same behavioral rhythm, and no significant difference was found in other behaviours. Adult tundra swan took on more vigilance tasks. The wintering swan spent most of their time to foraging (4547%). Foraging rate showed two peaks, one began from 9:00 am, foraging rate up to 7948%, another appeared in late afternoon 17:00. During the morning, swans showed a higher rate of flying behaviour, but in the other time of this day, it showed lower rate. Diurnal activity rhythm of wintering tundra swans, vigilance, resting, cruise and preening behavior kept a low percentage as 10%, while the percentage of standing and wingspreading behavior fluctuated at a very low level. There was no conflicting behaviour in this research.