【Objective】It is of great significance to explore genetic characteristics and evolution laws of the soils derived from Pleistocene sediments to the study of geological evolution and ancient climate change and the management of the soil resources. Chongqing is a region dominated by mountains and hills, and hence known as “Mountain City”, where the soil layer is thin, except for the soils derived from Pleistocene sediments, which are often quite thick in soil layer and hence high in land utilization rate, so it is the important agricultural resource of Chongqing. However, so far little has been reported on genetic characteristics and classification of the soils and effects of cultivation on evolution of their properties. Therefore, this paper addressed the issue in an attempt to promote development of quantitative classification of the soils, to provide certain theoretic bases and important ideas for rational utilization of the soils, relative to soil type. 【Method】Field soil surveys were conducted to specify six soil profiles, 3 upland soils and 3 paddy soils, derived from Pleistocene sediments of pebble-mixed yellow clay (PC), yellow clay (YC) and red clay (RC), of which soil morphological characteristics were obtained through investigations of their soil-forming environments. PC and YC (commonly known as old alluvial sediments) are mainly distributed on the high terraces on both sides of the Jialing River and its main tributaries, and RC mainly on the karst plains and some valleys in Xiushan County. Soil samples were collected from the profiles by horizon for analysis of physico-chemical properties. Based on the comparative analysis, genetic characteristics and classification of the soils relative to cultivation mode were discussed, and diagnostic horizons and diagnostic characteristics of the soils were determined, and the soils were attributed and named in CST level by level in the light of the “Chinese Soil Taxonomy (3rd ed.)”. 【Result】The upland soil derived from PC was found to have a lot of gravels but no iron-manganese speckles or stripes, while that derived from YC was found to be in a reverse condition and that derived from RC to have apparent clay deposition right beneath the plow layer. In the profiles of paddy soils derived from PC and YC, organic matter accumulation was obvious in the upper part, while iron oxide accumulation was in the lower part, so the upper part was lower the lower part in chroma. However in the paddy soil derived from RC, migration of iron oxide was not as obvious. The 3 upland soils were sorted into 3 subgroups, i.e. Typic Hapli-Udic Cambosols, Typic Ferri- Udic Cambosols and Red Ferri -Udic Argosols, and further into 3 soil families, i.e. Coarse bone loamy silica non-acid thermic -Typic Hapli-Udic Cambosols，Clay loamy silica mixture non-acid thermic - Typic Ferri-Udic Cambosols and Heavy clayey illitic mixture acid thermic - Red Ferri - Udic Argosols, separately. The 3 paddy soils were sorted into 2 subgroups, i.e. Typic Fe-accumuli- Stagnic Anthrosols and Typic Hapli- Stagnic Anthrosols, and further into 3 soil families, i.e. Clay loamy silica mixture non-acid thermic - Typic Fe-accumuli - Stagnic Anthrosols, Clayey illitic mixture non-acid thermic - Typic Fe - accumuli - Stagnic Anthrosols and Clayey kaolinitic non-acid thermic - Typic Hapli - Stagnic Anthrosols, separately. The six soils formed 6 soil series in total. 【Conclusion】The soils derived from YC have iron-manganese speckles or stripes, which are reflections of paleo-hydrological conditions, but now they are completely free from the influence of groundwater and no longer were the aquic soil moisture regime. The characteristics of sediments and regional climate do have some impact on clay deposition in the upland soils, thus affecting their classification on the soil order level. Long-term paddy cultivation would transform Cambosols and Argosols derived from Pleistocene sediments into Stagnic Anthrosols. Artificial activities, such as field screening, changing slopes into terraces, gathering pebbles et al, would reduce gravel content in the paddy soil derived from PC, which would in turn influence particle-size fractionation of the soil layers controlled by soil family.