<p>Most theoretical analyses of earth pressure in finite soils are typically conducted under either completely dry or fully saturated, homogeneous conditions, often ignoring the effects of matric suction and soil heterogeneity. In view of this, this paper employs the thin-layer element method to derive a numerical solution for the non-limiting active earth pressure in inhomogeneous soil under steady unsaturated seepage conditions, with the finite soil between adjacent foundation pits as the object of study. The model refines Coulomb’s earth pressure coefficient to account for the displacement of retaining structures on both sides of the finite-width soil, thereby enhancing its applicability to real engineering scenarios. Additionally, the development characteristics of wall-soil frictional strength under non-limit states were considered, along with the unsaturated soil strength criteria adopting the unified effective stress method that takes matric suction into account. This approach's validity is confirmed by comparing it with prior research results. Parameter analyses are performed to investigate the direct effects of key parameters on active earth pressure. The results show that finite width, inhomogeneous coefficient, empirical fitting parameters, and retaining structure displacement significantly impact active earth pressure. Consequently, it is crucial to consider the unsaturated seepage, soil heterogeneous, and non-limit states of the soil. These findings can be a reference for designing and constructing retaining structure in adjacent foundation pits.</p>