Abstract: Force measurements of a whole aircraft model with a delta wing and spanwise blowing were carried out and flow visualization of its semi-span model were conducted in the FL-8 and FL-5 wind tunnels. Several techniques, such as oil flow, water fog, helium bubble, fluorescent minitu-fts, were employed in the flow visualization.The comparative test investigations of two blowing techniques, i.e. the flap spanwise blowing and the blown flap, were completed with the identical model in the same wind tunnel.It is found that the flap shoulder vortex is generated over the flap instead of the jet vortex when the spanwise blowing is applied to a flap with large deflection angles. Furthermore, the flap shoulder vortex locates always ahead of the jet. Its vorticity originates from flap shoulder separation. Axial velocity of the vortex is provided by entrainment effect of the jet. It is also shown that the lift augmentation caused by the flap span-wise blowing should not be attributed merely to the boundary layer control and is mainly due to the vortex control.Lift increments originated from the flap spanwise blowing consist of two parts: one acts on the flap, another on the wing. The lift increments which approach to those of the blown flap are obtained at a small jet momentum coefficient（about 0.012） which can be provided by recent engines through selecting optimum configurations and parameters of nozzle. Therefore, it is possible to improve landing performance of aircraft markedly. For the first time a two-branch nozzle is applied, in result the flow over the whole surface of the flap is ameliorated.