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This study emphasizes to testify the potential of the Rb/Sr ratio of lake sediments as indicative of paleoprecipitation since 16 cal. Ka BP from a semi closed lake in Southwest China. Based on the study on the core LGH2 from Lugu Lake, we inferred that the Rb/Sr ratio of sediments in closed lakes is inversely correlated with precipitation and open lakes are positively correlated. In semi closed lake, the Rb/Sr ratio is always positively correlated with precipitation different from closed lakes.

According to the indicative significance of the Rb/Sr ratio, the paleoprecipitation evolution sequence in Lugu Lake basin since 16 cal. ka BP could be divided into six evolutionary stages: 1) the late glacial period (16.0-14.7cal. ka BP), the Rb/Sr ratio rose rapidly indicating that precipitation increased rapidly, and the climate had changed from dry to wet; 2) the Bolling-Allerod(BA) warm period (14.7-12.9 cal. ka BP), the ratio of Rb/Sr rapidly increased and remained high, indicating that precipitation increased; 3) the Younger Dryas (YD) period (12.9-11.6 cal. ka BP), the decrease of Rb/Sr ratio indicated that precipitation decreased; 4) the Early-Middle Holocene (11.6-3.5 cal. ka BP), the ratio of Rb/Sr was almost in the high value area, the precipitation was abundant, it was the warmest and humid period since the 16.0 cal. ka BP, the variation of Rb/Sr ratio indicated the climate was unstable, there are eight droughts (11.38-11.1, 10.35-10.22, 9.4-9.0, 8.39-7.66, 5.95-5.75, 5.3-5.06, 4.56-4.13 and 3.87-3.71cal. BP); 5) the sharp change drought period (3.5-3.0 cal. ka BP), the Rb/Sr ratio decreasing rapidly indicated that precipitation decreased suddenly, it had undergone about 500 years of drought event; 6) the Late Holocene(3.0cal. ka BP to 0), the Rb/Sr ratio reached lower value, and fluctuated four times greatly, indicating that precipitation, the lake water level decreased and the southwest monsoon weakened, there were four drought events: 3-2.82, 2.55-2.30, 1.3-1.1 and 0.43-0.25 cal. ka BP.

The variation of Rb/Sr ratio in sediments from Lugu Lake responses to the change of Asian monsoon driven by solar radiation since 16 cal. ka BP. It can also sensitively capture the influence of cold and dry climate from high latitudes, such as YD cold event, 8.2 and 4.2 cal. ka BP event, and also reflect the local regional climate feature, such as 3.5 and 2.5 cal. ka BP., which also proves that the delta O-18 value can indicate the change of local precipitation. Therefore, considering the closed and open state of lakes, it can be clearly and concretely explained the true implication of Rb/Sr ratio in Lugu lake sediment. However, it is prudent to use TOC to explain the climate change in semi-enclosed lakes.