The source area of the Yellow River (SAYR) is located in the transition zone between the Asian monsoon zone, the northwestern arid zone, and the alpine and cold zone on the northeastern Qinghai-Tibet Plateau (QTP). It is located in the catchment area above Duoshixia, approximately between 33°56'~35°31'N and 95°55'~ 98°41 'E, with an area of about 2.5 * 10~4km~2. Its fragile ecosystems and the simple structure of its natural environment are sensitive to climate change, making it an ideal region for global climate change research. Systematic study of climatic and environmental evolution processes and mechanisms in the SAYR is of vital importance for the exploration of response of permafrost environment to climatic changes on the northeastern QTP. A peat profile WLR (34°39'4.71"N,97°20′0.90"E; 4400m a.s.l.,480cm in length) was dig in October, 2014, which was 5km away from the Wanlongwama Lake, located in the south of the Tangchama Basin in the Lena River Basin in the south-central SAYR on the northeastern QTP. The maximum seasonal thaw depth of the active layer was about 80cm,and the average soil water content was 240% at depths of 80 ~480cm in the permafrost layer. 78 soil samples were collected from the bottom to the top of the profile at every 10cm between 480 ~300cm and at every 5cm between 300~0cm. In this study, the climatic evolution since 6. lcal.ka B.P. in the SAYR was reconstructed using the records of magnetic susceptibility, loss on ignition (LOI),and geochemical elements of the WLR profile. The results showed that the climatic evolution since 6. lcal.ka B.P. in the SAYR could be divided into four stages. The first stage was warm and wet during the period of 6.1 ~2. lcal.ka B.P.,and could be further divided into two sub-stages: from 6. lcal.ka B.P. to 5.4cal.ka B.P. the climate was warm and humid and from 5.4cal.ka B.P. to 2. lcal.ka B.P. it was cold and dry. In the second period, from 2. lcal.ka B.P. to 1.5cal.ka B.P., the climate was cold and dry; it was relatively warm and wet in the third period, which lasted from 1.5cal.ka B.P. to 0.8cal.ka B.P., and it has been warm and wet since 0.8cal.ka B.P. The climatic evolution process in the SAYR is highly unstable and has undergone century-millennial scale oscillations throughout all four periods. There have been six cold events since 6. lcal.ka B.P.: 6.1 ~ 5.8cal.ka B.P.; 5.4~3.9cal.ka B.P.; 3.0 ~2. lcal.ka B.P.; 1.9 ~1.5cal.ka B.P.; 1.3 ~ 1. lcal.ka B.P.; and 0.8 ~0.3cal.ka B.P. These evidently correspond with the cold events recorded by peat and lacustrine deposits and ice cores on the QTP, with peat deposits in low latitudes regions and with deep-sea sediments in high latitude regions in the Northern Hemisphere. The above results show that climatic change in the SAYR since the Mid-Late Holocene is consistent with global climatic change.