The pore throat microstructure is an internal factor that determines the physical properties of tight sandstone reservoir. Therefore，describing the characteristics of pore throat microstructure in a quantitative manner can provide a basis for studying on the quality characterization of tight sandstone reservoir. However，the micro-nano pore throats in tight sandstone reservoir are developed with strong micro heterogeneity，so it is difficult to accurately determine the characteristic parameters of pore throats by conventional experimental methods. In this paper，on the basis of high-precision digital core image（taking the SEM-Maps scanning image with resolution 10 nm as an example），a porous media model of tight sandstone is constructed. Furthermore，the paper has developed methods，including adaptive recognition and extraction of pore throats，the segmentation of pore throats based on image morphological algorithm，and the calculation of characteristic parameters of pore throat structure. In this way，the quantitative characterization of pore throat microstructure of tight sandstone based on the scanning image is realized. This paper selects three typical rock samples of tight sandstone from Chang8 reservoir in Honghe Oilfield in an attempt to calculate the characteristic parameters of pore throats quantitatively and to analyze the structural differences of pore throats. The results show that the physical properties of rock samples are closely related to the characteristics of pore throat microstructure and the more pore throat，the larger pore throat radius，the higher coordination number and the better connectivity of pore throat all make the permeability and other physical properties of rock samples better.