Abstract High mountains are humid islands in arid central Asia, and alpine vegetation is sensitive to climate change, especially to temperature variations. Here we present a palynological sequence and discuss the past vegetation and climate changes based on core BY10A from the Swan Lake, an alpine lake situated at an inter-montane basin in the central Tienshan Mountains, Xinjiang, northwestern China. We collected 52 modern pollen surface samples at different elevations to aid in the interpretation of fossil-pollen data, which provide a reconstruction of vegetation and climate history for the last 8.5 ka (1 ka = 1000 cal yr BP). Artemisia and Amaranthaceae (= Chenopodiaceae) are the main pollen types in desert steppe zone below 1800 m elevation, while Poaceae and Picea dominate the mid-elevation forest steppe zone (1800–2800 m). Cyperaceae is the main indicator of high alpine meadows (> 2800 m). From 8.5 to 6.9 ka, the vegetation was steppe meadow suggesting relatively warm climate. From 6.9 to 2.6 ka generally high values of Cyperaceae and peaty sediments indicate a fen environment and cooler, more humid conditions. Interrupting this mid-Holocene period is a 5.5–4.5 ka millennium of lacustrine sediments with lower Cyperaceae, higher Poaceae and Artemisia , and high values of Myriophyllum and Pediastrum indicating higher water levels and warmer temperatures. After 2.6 ka, pollen data indicate alpine steppe and warmer climate. The mid-Holocene pattern of cooler climate interrupted by a warmer period is consistent from other regional records from Xinjiang, including the Guliya ice core and Kesang Cave speleothem record. During the cooler periods, the regional record indicates that a weakened summer Asian monsoon is countered to some extent by a stronger winter monsoon.