In recent decades,shallow lakes in the middle and lower reaches of Yangtze River Basin (MLYB) are significantly influenced by climate change and human activities, probably rendering ecological regime shifts with degraded lake ecosystem services. Improved understanding of regime shifts and their transforming processes in shallow lakes is important for proper lake management. In this study, we focus on a typical big shallow lake in the MLYBChaohu Lake( 31°25'28"~31°43'28"N,117°16'54〃 ~117°51'46"E),and take use of diatom as the proxies to show the ecological regime shifts in lakes. Two sediment cores, C1 ( 31°35'47"N, 117023'58〃E) and C20 (31°32'08"N,117037'12"E) were taken with a piston corer in the deepest part of Chaohu Lake in 2007 and 2009, respectively. C1 core is the main core, conducting multi-proxies analysis (including chronology, TOC, particle sizes, elements and diatom) ; while C20 core is the supplementary one, conducting only diatom identification to compare with the results in C1 core. Besides, historical documents including climate change(annual temperature and precipitation),hydrologic data (dam construction and annual average water level),water resources (vegetation coverage, TP,TN and fish production),and social-economic data (GDP,cropland, population and consumption of fertilizer) in Chaohu Lake and its catchment were also collected. By combining historical documents and palaeolimnological records, the specific ecological regime shifts and its transforming processes were analyzed in Chaohu Lake since 1850. Results of diatom assemblages using STARS methods based on PCA scores of diatom in both C1 and C20 cores reveals that, at least a regimes shift took place in late 1970s in Chaohu Lake, showing high regime shift index at that time. Redundancy analysis (RDA) reveals that weakened hydrodynamics, increased nutrients and climate warming posed effects on Chaohu's ecological states in different time periods, rendering the loss of its resilience. However, increased inputs of nutrients were the main driving forces of the ecological regime shift, which made Chaohu Lake change into current turbid water state from clear water state. And not only that, climate warming further aggravated this change afterwards. By comparing the results of ecological regime shifts in Chaohu and Taibai Lake, which are typical big and small lakes in MLYB respectively, it shows that the driving forces of ecological state change and regime shift processes are different in above two lakes. That means targeted management measures are necessary to lakes with different size and characteristics on temporal perspective.