Abstract: A conventional annular exhaust ejection mixer and three lobed exhaust ejection mixers were tested at atmospheric pressure and low exhaust velocity conditions to study the effects of three structure parameters lobe exit angles α/β ,relative mixing length L/D and lobe penetration H/H_o on the aerodynamic characteristics of the lobed exhaust ejection mixers.The results show that the aerodynamic characteristics of the lobed exhaust ejection mixer are obviously better than those of an annular exhaust ejection mixer.The effect of the lobe exit angle α/β on the performance of the mixer is not so distinct if no separation occurs inside the lobes,but the increase of α/β is advantageous to the compromise between aerodynamic performance and weight.The increase of relative mixing length L/D can improve the aerodynamic performance.An optimum L/D exists for the compromise between aerodynamic performance and weight.The effect of the lobe penetration H/H_o on the aerodynamic performance of the lobed exhaust ejection mixer is significant.The enhancement of the lobe penetration H/H_o is advantageous to the flow mixing,but disadvantageous to the pumping ability.