Abstract: Taking the carbonate geothermal reservoir in Wumishan Formation of Mesoproterozoic Jixian System in Beijing as the research object, the micro-pore types of samples are classified with SEM visualization and slice identification, and the density and size development characteristics of micro fractures are quantified with the help of MATLAB image processing technology.The micro-medium-macro pore volume distribution of dolomite in Wumishan Formation is quantified by combining capillary force test and low-temperature liquid nitrogen adsorption experiment.Based on the macro porosity and permeability test results, the analysis concluded that the more developed microfractures, the more gas permeable pores and the better pore throat homogeneity, the greater the influence law of porosity and permeability, and the empirical relationship between porosity and permeability is fitted.Finally, a method of dividing favorable development intervals based on logging data is established.The results show that the connectivity of matrix pores of dolomite in Wumishan Formation is poor, and micro fractures and dissolution pores provide the main seepage channels.The overall pore distribution frequency is normally distributed with the pore size, which distributes at 50~60 nm most likely.The research results can provide basic data support for the development of geothermal resources in the Wuzhishan Formation in North China.