With the rise of unconventional oil and gas exploration, the study of shale reservoirs gets attention gradually and how to carry out the  research of the shale reservoirs has become the primary problem in the study of unconventional oil and gas. Research on the shale reservoirs has great significance to the layer selection in exploration of shale oil and gas, to the evaluation of resource potential and to the calculation of seepage capacity of oil and gas. The micro-nano pore characterization techniques of shale, the division of pore types in shale and the mechanism of porosity evolution in shale are respectively overviewed and evaluated, and available problems are pointed out by combining with the newest research progress. We propose that the industrial CT-micro CT-nano CT/FIB series of radiation scanning and pressure mercury injection (MICP)-nitrogen gas adsorption (N₂)carbon dioxide adsorption (CO₂) fluid method are the optimal methods of the quantitative characterization of reservoirs and the regression of experiment and porosity log should guide the favorite site of higher porosity. The classification of shale reservoir space should take oil and gas containing into consideration and AFM was suggested to study the reservoir continent ability for hydrocarbon. We suggest using rock diagensis simulation experiment and real profile samples to understand the shale porosity evolution and to find the main controlling factors with the aid of XRD analysis.