Ultra low permeability reservoirs are significantly affected by the pressure sensitive effect, resulting in severe permeability loss, leading to a larger starting pressure gradient and increasing the difficulty of establishing effective displacement. At present, the existing technical limit well spacing formulas only consider the static starting pressure gradient and do not consider the reservoir pressure sensitivity effect, which leads to the problem of dynamic changes in the starting pressure gradient, resulting in the calculation results not being consistent with the actual situation of the mine. In response to this issue, a formula for calculating displacement pressure near oil and water wells considering pressure sensitivity effect and a formula for calculating variable starting pressure gradient were first established. Combined with the traditional formula for calculating the maximum well spacing, a formula for calculating the maximum well spacing between injection and production wells that can establish displacement considering dynamic starting pressure gradient was derived. The relationship between the permeability of ultra-low permeability reservoirs in Chaoyang Gou Oilfield and the technical limit well spacing was calculated. The analysis results indicate that compared with traditional methods, the new method needs to reduce the well spacing by 10m; The technical limit well spacing of Y-3 block is 47m; The demonstration results and case analysis results demonstrate the correctness and applicability of the formula. The results of this article can provide theoretical guidance for infill adjustment and potential tapping measures in ultra-low permeability reservoirs.