In the development stage of the Upper Paleozoic He 8 Member tight sandstone gas reservoir in Sulige, a certain degree of water lock damage will occur, which in turn affects the productivity of a single well. By conducting water lock damage experiments on fracturing fluid and taking the real core samples of typical tight sandstone reservoirs as the research objects, combined with the low-field nuclear magnetic resonance (NMR) testing technology, the microscopic retention characteristics of immovable water were quantitatively evaluated, and the degree and laws of water lock damage within micro-nano scale pore throats were clarified. The experimental results show that there is a negative correlation between core permeability and the degree of water lock, and cores with low initial permeability and poor development degree of micro-pore throats are more likely to suffer from water block damage. There are significant differences in the water lock damage characteristics of cores in reservoirs of different qualities. The degree of water lock damage in Class Ⅰ and Ⅱreservoirs is lower than that in Class Ⅲ reservoirs. Class Ⅲ reservoirs retain more immovable water, and the degree of water lock damage is also higher. The retention rate of immovable water in micropores is highly correlated with water lock damage. Water lock damage mainly occurs in pores smaller than 50 nm, especially when the content of immovable water in pores smaller than 2 nm increases, it will significantly affect the permeability of the core. This study reveals the mechanism of water blocking damage in tight sandstone reservoirs in the Sulige gas field, providing theoretical guidance for enhanced production in tight sandstone gas fields.