<p>This study presents a closed-form pseudo-static limit equilibrium framework for evaluating the seismic internal stability of geosynthetic-reinforced soil slopes (GRSS), explicitly incorporating the effects of pre-existing tension cracks. The analysis considers the presence of water on both sides of the slopes, generating additional hydrostatic and hydrodynamic forces during seismic events. A key contribution of this work is the detailed quantification of how these factors, along with backfill soil and loading parameters, influence the minimum reinforcement demands required to maintain slope stability. Two cases are analysed: (1) in the absence of tension crack (<i>Z</i>_<i>c</i> = 0) and (2) in the presence of tension crack (<i>Z</i>_<i>c</i> ≠ 0). Parametric analysis shows that the presence of tension cracks increases the required reinforcement force coefficient (<i>K</i>) by up to 35 to 40% and reinforcement length by 20 to 25%. An increase in horizontal seismic coefficient (<i>k</i>_<i>h</i>) from 0.0 to 0.3 leads to increase in <i>K</i>, establishing <i>k</i>_<i>h</i> as the most dominant factor. In contrast, increasing cohesion (<i>c</i>) from 0.02 to 0.1 reduces <i>K</i> by nearly 50%, and raising internal friction angle (<i>ϕ</i>) from 25° to 45° decreases <i>K</i> by approximately 60%. The pore pressure ratio (<i>r</i>_<i>u</i>) also significantly affects stability, reducing factor of safety (<i>FS</i>) by 40 to 50% when increased from 0.1 to 0.4. A comparative validation with previous studies shows close agreement with their results. The paper concludes with practical design recommendations and discusses limitations of the pseudo-static approach, such as the assumptions of simultaneous peak loading and dry cracks. This framework offers a robust and conservative basis for the design of reinforced slopes in seismic and partially submerged environments, promoting more resilient and cost-effective geotechnical infrastructure.</p>