Using a unified measurement system with a suction control (UMS_SC), the soil-water retention curves and gas transport parameters (gas diffusion coefficient (D_p) and air permeability (k_a)) were measured for sands with different size fractions and particle shapes under drying and wetting processes. The gas transport parameters were generally higher for wetting process than those for drying process at the same soil-air content, indicating the formation of well-connected air-filled pore networks for wetting process. Higher percolation thresholds (soil-air contents where gas transport ceases due to interconnected water films) were observed for k_a measurements as compared to D_p measurements under both drying and wetting processes. Sand particle size and shape effects on the hysteretic behavior of both soil-gas transport parameters (k_a and D_p) will be further investigated and presented in this study.