Based on the past 50 years data,we made a time-series analysis of the relationships among water quality,hydrology (e.g.,water level fluctuation) and submerged macrophyte succession (e.g.,species composition,biomass and coverage) in Lake Erhai,with the aim to explore the primary driving factors for the succession of submerged macrophyte communities.The results indicated that submerged macrophyte communities had experienced phases as expending,summit and decline.Since the 1980s,the increasing load of external nutrients,deterioration of water quality,heavy algal bloom,simplification of submerged vegetation and decreased grazing pressure of herbival animals had fundamentally impacted on the evolution and distribution of the macrophyte communities in the lake.Meanwhile,the large fluctuation of water levels accelerated the shift from a clear-water state to a turbid one, along with a drastic decline of submerged macrophyte and extinction of some endemic species.Therefore,reducing the external loading of nutrients and a reasonably water level regulation are suggested as priorities for the management and restoration of Lake Erhai ecosystem.