The problem of genetic classification of yellow earths has been mentioned by the writer in the report "A Soil Survey on the Jiulong Mountain of Zhejiang Province". However, up to the present, some points regardW g the chara,oteristics, genesis, distribution or even physical and chemical properties of yellow earth still remains confused. It is worth studying whether yellow earth is the product of moist climate, or it is formed from the hydration of ferric oxide.It is suggested that yellow earth should be merged with the red earth into one great group of yellow-red earth in the classification system, in view of the failure to find significant criteria to distinguish the yellow earth from the red earth, the typical primart yellow earth has not been discovered in southern China, where only the secondary yellow-red earth derived from the paleo-red clay could be found. Some soils of yellow colour may be due to the mineral composntion of the parent rocks, but not the influence of humid climate. Under normal presanre and temperature conditions, the hydrated iron oxide is difficult to be dehydrated, and iron oxide is also difficult to be hydrated. Therefore in nature there exists neither a model formula of soil genesis as yellow brown earth-yellow earth-red earth, nor a soil zone of yellow earth. In the mountain areas of southern China,there is a wide distribution of the paleored clay soil, which greatly influence the forestation of this region. It is proposed that the classification of the yellow earth should be based on its soil genetic properties under actual condition, but not be over-stressed on its zonality. After all, the formation of red earth one yellow earth as well as their mutual changes still remain puzzling.