Profile distribution of pigments,organic matter,total nitrogen and total phosphorus were investigated in sediment cores of Changtan Reservoir.Combined with current water ecological monitoring data and climate change data for the last 50 years,the trophic state succession and primary productivity change process were revealed.The effects of human activities and climate change on primary productivity and algae succession have been discussed.The trophic state has experienced stable,slow increase and rapid increase stages.The variation trend of sediment pigments was consistent with trophic state.The predominant species of algae gradually evolved from dinoflagellates and diatoms into cyanobacteria and green algae.The change of hydrodynamic conditions due to dam construction and the growth of N and P input result in the increase of primary productivity and the succession of algae community.In the recent 50 years,climate change accelerated the succession of algae community,and dominant species of algae evolved into temperature-sensitive Cylindrospermopsis raciborskii.This study can provide a reference for the identification of water ecological succession and ecological security assessment in the reservoir without water ecological data.