Abstract: The Shaozhai red clay section(34°59'17.5"N, 107°46'26.5"E) is 120.25m thick and located near Lingtai County of Gansu Province. The present-day climate at Lintai is semi-arid with a mean annual rainfall of 500mm and an annual mean temperature of 8.6℃. This section is lithologically composed of three parts:the type loess-paleosol sequence at the upper part(0~13.7m), the red clays interbeded with carbonate layers at the middle part(13.70~95.65m) and the underlying water-reworked loess sediment(95.65~120.25m). In this study, 488 oriented samples at 25cm intervals were taken for Paleomagnetic measurements, 4811 samples at 2.5cm intervals were collected for magnetic susceptibility measurements, and 477 samples at 20cm intervals were selected from the upper and middle parts(0~95.65m) for chroma tests. Magnetostratigraphic results show that the M/G and Ga/Gi magnetic reversals are found at the depths of 4m and 35.5m, respectively. Extrapolation with accumulation rates suggest that the top and basal ages for the type eolian deposits in this section are about 2.48Ma B.P.and 5.23Ma B.P., respectively. The color of soil is mainly affected by hematite and goethite. These iron oxides mainly come from pedogenesis, the hematite appears red and the goethite is yellow-brown Therefore, the higher redness and yellowness values of red clay indicate stronger weathering intensity. The chroma results of the Shaozhai red clay section show that the values of redness and yellowness have a good correlation and also coincide with the pedogenic intensity, indicating that they are ideal proxies for reflecting the changes of East Asia summer monsoon intensity. The Shaozhai red clay formation can be divided into three parts on the basis of redness, yellowness and susceptibility. The lower part(5.23Ma to 4.80Ma)have the higher redness, yellowness and susceptibility values, which are about 8.77, 23.88 and 67.75×10-8m3/kg on average, respectively. For the middle part(4.8~4.4Ma), the average values of redness, yellowness and susceptibility are about 7.92, 21.94 and 65.8×10-8m3/kg respectively, which are relatively lower compared with those of the lower part. From 4.4Ma to 2.6Ma, the redness, yellowness and susceptibility gradually increase, ranging from 6.14, 20.79 and 30×10-8m3/kg to 13.12, 29.26 and 243×10-8m3/kg and with average values of 9.64, 25.11 and 102.01×10-8m3/kg, respectively. These results imply that the East Asia summer monsoon strengthened stepwise since 4.4Ma in the Pliocene, which may be related to uplift of the Tibetan Plateau and closure of the Panama Strait.