Reinforced soil is widely used in the field of civil engineering and there is a significant difference in performance and mechanism between small spacing reinforced soil (Geosynthetics reinforced soil) and mechanically stabilized soil. Based on the particle flow theory, a simplified model of small spacing reinforced soil structure is established, and the soil arch formation mechanism of fillers of reinforced soil and the influence of spacing between reinforcement materials is analyzed. Research results show that under small spacing conditions, due to the constraint effect of reinforcement materials, the soil near the panel forms a soil arch; When the spacing between reinforcement materials is too large, a stable soil arch cannot be formed. Because of the influence of soil arch, the lateral static earth pressure of the soil filler on the panel decreases with the decrease of the spacing between reinforcement materials and zero lateral static earth pressure can be obtained when the soil arch of the small spacing reinforced soil forms.