To meet the functional requirements of the Yangtze River electronic waterway chart and improve its display reality for relevant information about flow velocity,we propose a division method for the main and subcritical flow velocity area based on the requirement of ship navigation.The flow velocity is measured by the Acoustic Doppler Current Profilers (ADCP).Moreover,the influential factors for dividing the velocity area are studied,and the segmenting of river is realized by the method proposed.