Over a decade of oil and gas explorations in the Yan’an area have yielded a series of breakthroughs in documenting theupper Ordovician Majiagou Formation, an important layer for natural gas exploration.This is the main sedimentary area of the Ordovician carbonate- gypsum rock symbiotic system, in which the M543- M532 gypsum deposit of the upper Majiagou Formation is a typical representative of the regressive evaporative environment. Based on the latest results from the development of Ordovician gas exploration in the Yan’an gas field, utilizing datafromcore observations, experimental analysis, drilling and logging, and on the basis of sedimentary structure, the scale of gypsum- salt rock development, lithologic assemblage and the geological characteristics of gypsum- salt rock assemblage in the Majiagou Formation in the study area are elaborated. Finally, the sedimentary background, sedimentary facies and sedimentary evolution model of the assemblage gypsum- salt rocks in the Majiagou Formation in the study area are systematically summarized. The results indicate thatagainst the background of sedimentary pattern of high west and low east, stratum filling is characterized by thin west and thick east, thin south and thick north.The gypsum dolomite- gypsum- salt deposit area extends from southwest to northeast. Three types of rock assemblages were vertically developed: type I gypsum dolomite- anhydrite nodule dolomite- gypsum dolomite- mudstone assemblage; type II gypsum- anhydrite nodule dolomite- gypsum dolomite- mudstone assemblage; and type III salt- gypsum- anhydrite nodule dolomite- gypsum dolomite assemblage. It is a relatively quiet and low- energy lagoon sedimentary model. There is evolution of sedimentary environment into extreme evaporative salinization- evaporative gypsum- relative openness. The research results can be used as reference for geological research into the Ordovician gypsum salt rock in other areas of Ordos Basin and also provide important guidance for oil and gas exploration in the Yan’an gas field.