This paper deals with clay minerals and primary minerals of soils which developed on sediments on the terraces and valley flat of ferent periods Wushui,the North River,Hengshishui and Lian River in Northern Guangdong.The result obtained showed that disparity in mineral composition depended upon differetzt sources of sediments in river valleys.In the same river valley,composition of soil minerals in the third terrace (T_a) which was developed from the Early pleistocene differed greatly from that in other terraces.It resulted from different conditions of weathering and soil formation and different sources of sed.imentary matter.In the Second terrace (T₂),the First terrace (T₁) and the valley flat (T_o),the composition of soil minerals were similar and sedimentary matter was basically the same,only weathering degree was different.The higher the terrace and the older the age of soil formation the stronger the allitic degree was.However,the disparity degree among the terraces was not the same.Because of time factor combined with climatic fluctuation T,diffened greatly from T₂ but less from T_o.