The responses of sand columns internally reinforced with horizontal geotextile layers are studied using a numerical method. The sand in the column is modeled using a non-associated plasticity flow rule. The numerical results are validated through laboratory triaxial compression tests carried out on sand columns 70 mm in diameter and reinforced with 4, 6 and 8 layers of geotextile. Numerical and experimental results are compared for deviatoric stresses and volumetric strains. The numerical analysis also provides an insight into the reinforcement mechanism. The factors affecting the reinforced column response and the advantage of horizontal reinforcement are outlined. Parametric studies on the influences of reinforcement properties, reinforcing layer spacing and specimen diameter as to the response of reinforced sand columns are examined. The numerical results show reinforcement has a significant influence from the edge toward the center of the column. The boundary makes a constant inclination angle with the reinforcement. For the reinforced column with low spacing/diameter ratio, the stresses in the influenced areas developed from the two consecutive reinforcements overlapping and the effects compounded. The lower the spacing/diameter ratio the greater the column reinforcement strength improved. An advantage of horizontal reinforcement is reinforcement rupture or soil-reinforcement interfacial slippage will not cause dramatic collapse of the entire column.