Molt is one of the three major life events in the annual cycle of migratory birds, but has historically received less attention than breeding and migration. Research on molting and habitat use while molting is still lacking for most large bird species, especially cranes. From May to August 2018, we tracked n = 40 White-naped Crane (Antigone vipio; n = 21 adult birds during the flightless period, n = 19 juveniles born in 2018) in the wetlands along the Kherlen and Ulz Rivers in eastern Mongolia. Our field surveys found that White-naped Cranes lost their primary and secondary feathers simultaneously during molting. Using the time-series clustering method, we found the flightless period of White-naped Cranes lasted from July to August, with an average duration of 17 days. Only some individuals molted flight feathers in consecutive years. Adult females molted earlier than males, and breeding individuals molted after the eggs hatched. The molting duration of sub-adults was slightly shorter than of adults.