Flow active control on transport aircraft after-body flow separation by the spark jet was numerically studied. The results show that the spark jet directly supplied the high-energy momentum to the boundary layer of the separation zone. Vortices induced by spark jet strengthened the mixing between the high-speed main flow and the low-speed boundary flow. It delayed the separation of the after-body flow and reduced the size of the separation zone. Under the same spark jet parameters

the effect of active control was better when the spark jet was led into the boundary layer at the position of the separation point or the downstream separation point. The average drag coefficient was reduced to 3.26%. Compared with the mass equivalent steady jet

pulsed jet and the pulsed jet had better performance on drag reduction than the steady jet. The spark jet was superior to the pulsed jet on drag reduction.