Abstract: The understanding of the origin and distribution characteristics of the deep buried Cambrian dolostone reservoirs in Tarim Basin is the key to searching for high quality reservoirs. The types and origin of the Middle-Lower Cambrian dolostone reservoirs in Tarim Basin are studied based on the analysis of outcrops in northwest Tarim Basin and key drilling data. The results show that the Middle-Lower Cambrian reservoirs in Tarim Basin are divided into microbial dolostone reservoirs and dolo-grainstone reservoirs; and microbial dolostone reservoirs can be further subdivided into cysto-like dolostone, stromatolite dolostone and thrombolite dolostone reservoirs. It is found out that, firstly, the formation of pores was controlled by high-energy deposits and early diagenesis; shoals and microbial mounds were characterized by such abundant primary pores as intergranular pores and microbial framework pores, which were important prerequisites for the development of high-quality reservoirs. Secondly, high-energy deposits were also more prone to being completely occluded by sea water-derived cements during early diagenetic stage, thus making it critical for high-energy deposits to be exposed to penecontemporaneous meteoric dissolution resulting from high-frequency relative sea level changes. When high-energy deposits with high primary and secondary porosity were gradually buried to the present depth, the preservation of porosity of the Middle-Lower Cambrian dolostone reservoirs was attributed to early massive dolomitization and rapid sealing effect of the overlaying thick evaporites. Besides, owing to episodic faulting-related intraformational and hydrothermal fluids, abnormal diagenetic alteration of dolostone, such as intense recrystallization, dissolution, silica and saddle dolomite cementation, resulted in the reconstruction of reservoir space, and locally destroyed and increased the reservoir heterogeneity.