Abstract: This paper systemically measured the proxy indices of the summer monsoon from the loess-paleosol sequences in the red clay sequences of the Xifeng profile, Gansu Province, including the values of magnetic susceptibility (MS) and frequency dependent magnetic susceptibility, and the contents of carbonate, organic matter and free iron oxides. We reconstructed the change characteristics of the paleoclimate by the carbonate contents and the values of magnetic susceptibility. The results showed that the frequency dependent magnetic susceptibility and the contents of organic matter and free iron oxides are positively correlated with the magnetic susceptibility, while the carbonate contents are negatively correlated with it. All these features can be regarded as the proxy indices of the summer monsoon. The paleoclimatic change of the whole Quaternary by the mathematic model could be divided into three periods: 0~1.1 Ma BP, 1.1~1.9 Ma BP and 1.9~2.6 Ma BP. The annual mean precipitation and annual mean temperature decreased obviously since 0.1Ma BP, which indicates that the climate will be more and more dry and cold in the future.