A self-developed laser processing system consisting of discrete designed transformation module and reflected ring focusing module is employed to re-melt the inner face of small-bore tube, and the macro appearances and microstructures of remelted layers are analyzed in details. The results show that the processing system can re-melt the inner face of the small-bore tube with diameter below 30 mm without a rotating mechanism. The quality of remelted layer is good without spiral overlapping edges and ripples under the optimum processing parameters. The molten pool is ring-shape and the cracking tendency is remedied obviously. The penetration of remelted layer increases first and then decreases with the increase of the number of laser scanning, and the penetration and surface toughness reduce with the increase of scanning speed.