NSM-CFRP strip cannot be wrapped around the column, the necessity for flexible near-surface mounted carbon fiber reinforced polymer (NSM-CFRP) material has recently arisen. Under concentric compression stress, twelve circular reinforced concrete columns (RC) with three slenderness ratios (17.3, 23.8, and 28.1) in addition to the spacing between ropes were investigated to assess the behavior of confined RC columns using NSM-CFRP rope. The results showed that the load capacity of RC columns was increased by using the NSM-CFRP rope and decreasing the spacing between the NSM-CFRP ropes. Furthermore, when the slenderness ratio is decreased, the load capacity of columns increases. Specimens with heights of 800 mm, 1100 mm, and 1300 mm reinforced with 150 mm spacing between CFRP ropes had a greater increase in capacity (3.3 times, 1.6 times, and 1.97) than control specimens of each height. The confinement technique using spiral CFRP rope at 150 mm spacing has the greatest impact on the load-carrying capacity of the RC column. Additionally, confining the RC column with spiral CFRP rope at a 150 mm spacing enhanced the bearing load capacity of the RC column with the lowest slenderness ratio more than the other slenderness ratios. Finally, when the slenderness ratio increases, the bearing load capacity and axial strain corresponding to the maximum axial stress decrease. The slenderness ratio had the greatest impact on the behavior of the RC column when there was a higher amount of CFRP rope or when the spacing between CFRP ropes was the lowest.