The accuracy of T₂ cutoff directly affects the accuracy of nuclear magnetic resonance calculation of bound fluid saturation, movable fluid porosity, and permeability. The pore structure of deep dense sandstone reservoirs is complex, characterized by low porosity, low permeability, and strong heterogeneity. The applicability of fixed T₂ cutoff values is poor. To improve the calculation accuracy of T₂ cutoff value in deep tight sandstone reservoirs, this study relied on nuclear magnetic resonance experimental measurements of deep tight sandstone samples and constructed a T₂ cutoff value calculation model that integrates Gaussian function and reservoir classification multi parameter fitting method. Program this model to achieve point by point calculation of T₂ cutoff values for deep tight sandstone reservoirs in offshore X zone. The research results indicate that when the bound water saturation is less than 41%, the Gaussian function method has higher accuracy in calculating the T₂ cutoff value, but when the bound water saturation is greater than 41%, the Gaussian function method is no longer applicable; For class Ⅱ and Ⅲ reservoirs (with bound water saturation greater than 41%), the T₂ cut-off value multi parameter fitting calculation model constructed using optimized sensitivity parameters has high accuracy; The T₂ cutoff values calculated by the fusion of Gaussian function and reservoir classification multi parameter fitting method are highly consistent with those determined by rock sample experiments, fully meeting the needs of nuclear magnetic resonance logging to evaluate pore structure in deep tight sandstone reservoirs.