Abstract: We reported the design optimization of pneumatic conveying system,a subproject of the high-speed Martian dust-storm wind-tunnel,which simulates the realistic Martian environment for evaluation of China's Mars probe.The original work was the secondary wind injection proposal,in which the primary nozzle injects a mixture of CO₂ and dust; the secondary nozzle-array injects CO₂ only for triple purposes: including further increasing flow-rate,initiating well-defined circulating dusty wind and minimizing turbulence in wind tunnel.The major variables,including but not limited to the conveying pressure/mixing-ratio/speed,mass flow-rate,pipe-diameter and secondary air volume,were optimized via extensive literature search,by experimental data analysis,in numerical simulation and in theoretical calculation.We suggested that the design optimization of pneumatic conveying system be of some basic and technological interest for the development of China's high-speed Martian dust storm simulator.