This study presents a closed-form solution for the internal stability analysis of geosynthetic-reinforced steep soil slopes (GRSS) under seismic loading, utilizing the pseudo-static approach within the framework of the limit equilibrium method (LEM). The primary objective of the steep slope design is to extend and raise the natural terrain to support the construction of road pavement. The analysis evaluates slope stability against both tension and pullout failure modes, considering factors such as backfill inclination, water levels on both sides of the slope, and the influence of tension cracks at the top surface. The model incorporates the effects of hydrostatic and hydrodynamic pressures in partially submerged and fully saturated backfill soils, as well as the impact of tension cracks. Key parameters investigated include variations in seismic acceleration coefficients, slope angle, internal friction angle (ϕ), water height, pore pressure ratio, cohesion, and surcharge loading. Based on the analysis, the minimum required length of geosynthetic reinforcement for each layer is determined to ensure stability under the additional forces induced by seismic activity. The results demonstrate that an increase in cohesion and ϕ significantly reduces the required reinforcement length, whereas increases in surcharge loading, seismic acceleration coefficients, pore pressure ratio, and water height necessitate longer reinforcement to maintain slope stability. Additionally, the presence of tension cracks shortens the failure plane, further increasing the reinforcement demand to prevent failure. The results obtained from present study are validated through comparisons with existing literatures.