Dianchi Lake (25°04 N,102°41’E ),lying to the south of Kunm ing City·the capital ofYunnan Province,is an ideaI field for studying the evolution of the Southwest M onsoon.The core D93-l is sampled in the Iake at the depth of 4.05m.The ¹⁴C ages at 0.65m. 1.7m,2,65m and 3.95m are 1 670± 1 40aBP,4540± 220aBP,6700± 160aBP and 2900± 1100aBP respectively. The sediment rate of upper layer determ ined by ²¹⁰Pb and ¹²⁷Cs measurement was about 1.78mm/a after 1948A,D.,and lmm/a for the Iast 250 years,Meanwhile.such environmentaI proxies as pollen assemblage.totaI organic carbon(TOC). Total nitrogen(TN)+(C/N),¹³C_org,magnetic susceptibility (X)and frequency dependent m agnetic susceptibility (X fd)·have been used to restore the history of environm ental evolution in the lake area since 13kaBP.As a result,Dianchi Lake has undergone the following clim atic variations since 13kaBP; 13-10kaBP.it was cool and wet;l0-7.5kaBP.it was a transitionaI period while clim atetransited to warm and wet and Iake water leveI becam e higher. 7.5-4kaBP.it was warmand wet with little variation. The highest temperature em erged about 6.5kaBP,4-2,7kaBP,the clim ate changed to cool and dry,suggesting an abrupt change in environm entalproxies,2,7-1.7kaBP+ all environmental proxies exhibited the characteristics of slightwarm and wet climate, and, lake area enlarged with lake water level uprising, Since1.7kaBP human activity has m ade a notable impact on the environm entaI evolution.