Due to uneven soil conditions, buildings on hillsides with split foundations face unique seismic design challenges. This study examines the effectiveness of high-damping rubber bearings (HDRBs) using the Deformation History Integral (DHI) model to accurately simulate the complex nonlinearity of HDRBs and mitigate seismic risks. Nonlinear time history analysis was performed on three configuration structures: non-isolated split Foundation (SF), split foundation isolated (SFIS), and split foundation middle-story isolated systems (SFMIS) across varying earthquake intensities. Results indicate that non-isolated structures (SF) exhibit the highest base shear and overturning moments, highlighting their seismic vulnerability. SFIS models show moderate improvements, with reduced base shear and enhanced stability. SFMIS models demonstrate significant reductions in base shear, maximum inter-story drift, and overturning moments, underscoring their superior effectiveness in seismic mitigation. Incorporating HDRBs, modeled with the DHI approach, reveals effective energy absorption and dissipation, resulting in lower peak accelerations, inter-story drifts, and maximum story displacements in isolated structures. The stable hysteresis behavior with higher strain stiffening increased the energy dissipation capacity of HDRBs, significantly enhancing the seismic resilience of hillside buildings. These findings emphasize the crucial role of isolation systems, particularly middle-story isolation, and the significance of DHI modeling techniques in enhancing the safety and stability of hillside structures during seismic events.