Cross flow transition is requested to delay since it gives rise to an increased friction drag for a swept wing. At a very low turbulent intensity of the incoming flow, say 0.08%, standing vortex mode with a characteristic wave length dominates the cross flow transition. Hence, modifying the standing vortex mode can be expected to delay the cross flow transition. In this work, a 3-D discrete rough elemental array is adopted to change standing vortex mode by mean of changing the characteristic wave length and amplitude of the standing vortex. Finally, one may reach the aim to delay cross flow transition. The experiments were conducted in a low-speed wind tunnel with a square working section 1.2m×1.2m×3m. The turbulence intensity is 0.08%. The 1.2m chord length NLF-0415 airfoil, with 45° swept angle and the attack angle of -4°, was chosen to study cross flow transition (Fig.1). The Reynolds number based on the chord length is 1.2×106 ~ 3.0×106. Figure 2 shows that boundary velocity profile obtained by hot wire along the red line at X/C =40. For Re = 1.2×106, there are no apparent characteristic wave length. For Re = 3.0×106, an apparent characteristic wave length is about 8mm. Another evidence is obtained by naphthalene sublimation flow visualization (NSFV) technique. According with that, three center-to-center spacing of the elements, 4mm, 8mm and 12mm respectively, were used to disturb the standing vortex. Twenty 3-D rough elements being an array are printed at 4% chord length from the leading edge. Each element is a micro-circular cylinder with the diameter 1mm and the height of 50μm (Fig.3). The NSFV measurements show that the cross flow transition can be severely delayed, from X/C = 0.45 to the ending tail of the airfoil for the case of 4mm spacing at Re=3.0×106 (Fig.4). However, for 8mm and 12mm spacing, the flow transition keeps same as the natural case. In the full paper, velocity profiles will be given and to interpret why the short spacing may result in more functional effect on the cross flow transition.