During drilling operations, drilling fluid will invade the reservoir due to pressure difference and cause damage, affecting the productivity of oil and gas wells. This article selects sandstone cores of three permeability levels and two drilling fluid systems as the research objects, and conducts drilling fluid invasion damage evaluation experiments on the cores, including damage evaluation of different intrusion pressure differences, core damage evaluation of different permeability levels, and different drilling Damage evaluation of sandstone caused by fluid system, etc., to analyze the damage caused by drilling fluid to tight sandstone. Finally, the drilling fluid damage mechanism was analyzed based on microscopic morphology, three-dimensional reconstruction and nuclear magnetic scanning. Experimental results show that: in the same core, the greater the intrusion pressure difference, the greater the damage to the drilling fluid; the greater the sandstone permeability level, the higher the drilling damage rate; potassium-ammonium-based drilling fluids are more damaging than polyamine drilling fluids; drilling fluids. Intrusion enhances the hydrophilicity of the rock surface, resulting in enhanced invasion dynamics. At the micro level, it was found that drilling fluid materials adhere to the mineral surface or partially block the pore channels, and the permeability and porosity are reduced; according to the three-dimensional reconstruction analysis, the proportion of drilling fluid invading the proximal end is as high as 60% compared with invading the far end; mercury injection. The data shows that the porosity decreases to varying degrees after the invasion of drilling fluid. The experimental results have certain reference significance for on-site drilling research on reservoir protection strategies.