陕甘宁盆地中部气田中区马家沟组五４段白云岩类型多样，文章重点研究了泥微晶白云岩类和粉细晶白云岩类的矿物学和地球化学特征，在此基础上讨论了白云岩的成因，认为泥微晶白云岩为准同生期超咸水白云化成因，粉细晶白云岩为成岩早期混合水白云化成因。并根据白云岩中储集空间类型的分布讨论了各类白云岩的储集性。 There are various types of dolomite in Ma4 4 section of Majiagou Formation in the middle part of the Central Gansu-Ningxia Basin. This paper focuses on the mineralogical and geochemical characteristics of mud microcrystalline dolomite and fine grained dolomite. On this basis, The origin of dolomite is that the mud microcrystalline dolomite is the genesis of hypersaline water dolomitization in the quasi-contemporaneous period, and the fine-grained dolomite is the cause of dolomitization of early mixed water in diagenesis. Based on the distribution of reservoir space types in dolomites, the accumulations of various dolomites are discussed.