通过对鄂尔多斯盆地彭滩一杨井地区长21层段岩心的观察和薄片、粒度、测井相等基础资料的分析，指出鄂尔多斯盆地彭滩杨井地区三叠系长21层段属曲流河三角洲平原亚相沉积，其可详细划分为水上分流河道、决口扇、河漫滩、河漫沼泽和河漫湖等6个微相，其中水上分流河道和河漫滩微相最为发育；同时对长21层段各小层沉积微相的古地理展布与演化特征进行了分析并提出了沉积模式，认为油气的聚集受沉积微相的控制，水上分流河道砂和河漫滩泥为长21层段良好的储盖组合，是研究区油气勘探的方向。

By analyzing the data of drilling cores, costing thin sections, image granularities as well as logging, it indicated that deltaic-plain meandering river deposition is the main sedimentary system of Chang 21 in Pengtan-Yangjing district. This text marks off six microfacies such as upper-river channel, crevasse, overbank, overbank-splay, overbank-marsh and lake microfacies. And the upper-river channel sandbodies were developed widely. The evolution and the distribution of the microfacies in every number have been studied,and also builted the deposition model. The accumulation of oil and gas are controlled by microfacies. The upper-river channel deposit of Chang 21 is the good reservoir, and also is the direction of the developing in.