In order to investigate the influence of different parameters on displacement boundaries in ultra-low permeability reservoirs, According to different properties, the influencing parameters were divided into three categories: macroscopic category, anisotropism category, and radius category. The Pearson correlation coefficient method were used to calculate the correlation between different parameters and the movable fluid saturation and the cut-off radius. The results show that among all parameters, porosity and permeability have the highest correlation with the movable fluid saturation, while variation coefficient and median pore-throat radius have the highest correlation with the cut-off radius. It is concluded that in ultra-low permeability reservoirs, the main factors affecting the movable fluid saturation are macroscopic category, and the main factors affecting the cut-off radius are anisotropism category and radius category.