Aerated drilling is an important technical method for exploring and protecting oil gas reservoir, controlling mud loss in reservoir with natural fractures, and improving the rate of penetration. This paper expounds fluid patterns of gas-liquid two-phase flow in annulus and drillstring while drilling, which is derived from many experimental data and computing research. Meanwhile, Aerated drilling fluid wellhole flow mechanics model and numerical solution were established. And the gas-liquid flow rate design charts forφ216mm wellhole in conventional well structure were calculated and plotted, which have contributed to field operation and engineering design. The flied aerated nitrogen drilling experiment in Baiquan-1 well’s fracture Tight Reservoir have completely confirmed that the new the gas-liquid flow rate design charts have been satisfied for nitrogen aerated Underbalanced drilling engineering design and flied operation, and the drilling technology have many characteristics including stronger formation adaptability, larger pressure control range, smaller scare of special equipment, simper drilling process.