Based on 13 wells and 2 outcrops,the characteristics and geneisis of dolomite reservoir of the Lower Cambrian Xiaoerblak Formation in Tarim Basin are studied. It is indicated that micritic dolomite, powder-fine crystal dolomite, algal dolomite(or microbial dolomite) are the main dolomite types of Xiaoerblak Formation. The development of porosity is related to lithofacies obviously. Through the analysis of rock features and multi-parameter geochemical characteristics, and combining with the geological background, the diagenesis sequence and the pore evolution history of dolomite reservoir in Xiaoerblak Formation were studied and the main controlling factors of dolomite reservoir were proposed as follows: Porous sediments of high-energy reef-shoal(mound) facies are the material basis of reservoir development;Dissolution of metrical water in early supergene stage is the key factor to reservoir formation; In addition, burial (hydrothermal) dissolution can improve the reservoir quality.