Total organic carbon (TOC) content of lacustrine sediments has been widely used in the climatic and environmental studies as a proxy of productivity in the catchment and lake water; it is also used as an index of monsoon precipitation in the regions dominated by the Asian summer monsoon. In the present paper, we summarized the variation characteristics of TOC in Lake Qinghai sediments at scales of past millennium, the Holocene and the glacial-interglacial; and discussed the sensitivity and applicability of TOC for indicating climate change. The results indicate that the variation of TOC in Lake Qinghai sediments during the past millennium is consistent with that of regional warm season temperature, as well as the precipitation. After compared with regional summer temperature, pollen-based precipitation reconstruction results, and moisture evolution inferred from water level of lakes and aeolian activity history, we found that TOC content or flux cannot be regarded as a reliable index of the intensity of summer monsoon or monsoonal precipitation during the Holocene. TOC content from Lake Qinghai during the Holocene and the last glacial were distinctly different, indicating huge difference of precipitation and temperature at the glacial-interglacial scale. Therefore, the sensitivity of TOC in lake sediments to climate change is different at different places or different time scales; it should be very careful to use lacustrine TOC as an index of Asian summer monsoon intensity, especially in the cold and high-altitude regions.