Abstract: Nano-scale and micro-scale pore throats dominate the unconventional tight oil and gas reservoirs. Pore-throat microscopic structure is a key factor to lead to the low-permeability and low-porosity reservoir features. It is also the foundation to establish the criteria for evaluation of unconventional oil and gas reservoirs and interpret the basic geologic features, such as hydrocarbon occurrence and accumulation. Currently, microscopic pore-throat characterization techniques for unconventional tight oil and gas reservoir are based on nanoscale material science, physical chemistry and analytical chemistry. Initial progress has been made in the study of pore size, morphology, distribution and 3D connection by means of direct image observation under field-emission scanning microscope, indirect numerical value measurement such as gas absorption, and 3D value reconstruction modeling pore structure by X-CT, improving the characterization accuracy of nano-scale microscopic pore-throat structure. However, more efforts are required to improve pore-throat structural characterization techniques in the areas of principle testing, integration of multi-data, combination of multi-techniques and pre-experiment disposition, and multi-scale feature characterization. This study will provide the data for precise evaluation of favorable tight reservoir, tight oil and gas zones and other unconventional hydrocarbon sweet spots.