Paleosalinity of Tianluoshan Site is reestablished by mensurations and analyses of clay mineral, boron, strontium, barium, after sampling in a profile of Tianluoshan Site. The relative sea level changes are discussed according to the lab results. It turns out that there are at least three time periods of relative sea-level highstand not only before but also during and after Hemudu Culture in Tianluoshan Site. Based on previous researches and through studying several environmental elements comprehensively, the characteristics of environmental background and their relationships between human activities and development of Hemudu Culture are systematically discussed.