Sediment core samples were collected in Shuanglong reservoir to the south of Dianchi Lake. Sedimentary history was analyzed by ²¹⁰Pb dating method; the distribution characteristics of granularity of sediment cores, total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) were investigated; the relationship between environmental parameters and socio-economic parameters of Kunming were established. The results showed that: 1) the granularity of sediment cores ranged from 4.07 μm to 6.90 μm, with an averaged value of 5.71 μm. The granularity of sediment cores decreased after 1986. 2) The averaged concentration of TOC, TN and TP were 11.30 g/kg (ranging from 8.78 to 26.15 g/kg), 2.01 g/kg(1.59 to 3.26 g/kg) and 0.33 g/kg(0.23 to 0.47 g/kg), respectively. The contents of TOC, TN and TP were relatively stable before 1998. However, the three indicators increased rapidly after 1998. 3) Organic index and organic nitrogen were employed to evaluate the water quality, the results showed that there are accelerate increase trends in both of the indicators. 4) Linear correlation was observed between TOC concentration versus gross domestic product(GDP), organic index versus GDP, and increasing TOC concentration had a significant correlation with population, as well as organic index versus population, respectively. The results indicated that water ecological parameters were significantly affected by socio-economic parameters, human activities are major factors influencing the water quality of Shuanglong reservoir in recent decades.