Glacial lakes distribute widely in the alpine mountains on the southeastern Tibet Plateau. Lake sedimentary process in this region is synthetically controlled by regional climate change, hydrological and geological conditions in the catchment, and lake morphological feature. To gain a more comprehensive understanding of lake sedimentary process, a 480 cm long core BSCW-1 was collected from the deepest part (120 m in depth) of the Lake Basomtso on October, 2012. The top 90 cm was used in this study to reveal the sedimentary process over the past 200 years. The chronology was constructed based on ²¹⁰Pb/¹³⁷Cs measurements from the upper 60 cm and one AMS ¹⁴C result at 90 cm depth. Physical (grain size, sorting coefficient) and chemical data (TOC, TN, C/N) were measured and analyzed. These data reveal a remarkable transition in sedimentary process between the late 18th and 19th centuries, showing abrupt decrease in sedimentation rate. By comparing tree-ring-based climate reconstructions (temperature, precipitation and relative humidity) and records of palaeoglacial investigation, we suggested that regional climate change and glacier distribution in the catchment together influenced the sedimentary process in Lake Basomtso. Given that glacier had extended to lower altitude during the late 18th century, the following rise in temperature may have intensified meltwater which can transport more coarse particles into the lake basin. Along with glacier recession, the headwater moved gradually away from the lake, which caused finer particles depositing in the lake. In addition, the impact of geological event on sedimentary process cannot be excluded because this region is located in the orogenic belt. Fossil diatom has been a practical approach for climate and environment research. Diatom record from Lake Basomtso reflects moderate species turnover (DCCA=0.47 SD), indicating that diatom assemblage had not passed the ecological threshold over the past two centuries. This phenomenon is consistent with other diatom records from lakes on the southeastern and eastern Tibet Plateau. The ratio of planktonic to benthic species abundance (P/B) is relatively low between the 1770s to the early 1900s, which corresponded to the distinct coarse-grained sediments in core BSCW-1, implying some connection between sedimentary process and fossil diatoms. Additionally, although the nMDS, Procrustes and Protest analysis reveal modest similarity between diatom and grain size datasets, the lower Procrustes residuals between 1770-1901 AD support the argument that sedimentary process has some impacts on fossil diatom record. High-energy fluid with high velocity and strong sand-carrying ability can wash and carry more lotic and littoral diatoms into the open water (or the profundal zone) then deposit in the lake center. Since benthic diatoms are dominated in rivers and shallow waters, decline in P/B ratio is a reflection of enhanced hydrological and sedimentary conditions given that lake water level varied little during the past two centuries. As most lakes on the southeastern Tibet Plateau are strongly influenced by glacier and geologic activities, we suggested to consider the effect of sedimentary process and recommend multi-proxy analysis when using biostratigraphic data to interpret climate and environment change in this region.