Abstract: Lantsang river source is located in the north Tanggula Mountain of Qinghai-Tibet Plateau, nearby the south source of the Yangtze River, with hardly any human activities. In order to gradually recognize Lantsang river geomorphology and obtain basic data of geomorphology evolution of river, as well as scouring and silting process of riverbed, we carry out in-situ investigation and collect data and images to judge the river pattern of Moyun reach in Zhanaqu river, west source of Lantsang river. The results show that, boundary constraints of Moyun reach are weak with poor stability of riverbed; furthermore, in the classification system of river pattern which consists of 4 kinds, namely straight, meandering, anabranching, and wandering, we uniformly determine the reach is wandering type by using different discriminants; meanwhile, in the classification system of river pattern with 3 kinds, including straight, meandering and braided, we regard the reach as braided type; finally, according to domestic river characteristics and current classification system, we conclude that Moyun reach is wandering type. Field observation data and river pattern discrimination offer reference for further research on the river geomorphology of Lantsang river source.

Key words: Lantsang river, river source, river geomorphology, river pattern discrimination, wandering river pattern