At present, the gas reservoir of Dengying Formation in Gaomo is in the early stage of development. The distribution of fracture cavity body is complex and the heterogeneity is strong. Due to the liquid accumulation at the bottom of the test well and the poor physical properties of the reservoir in the far well area of most gas wells, the flow state of conventional back pressure test well can not reach stability under the larger production system, and the productivity test results are greatly different from the actual situation. Based on binomial deliverability equation of gas well and iterative operation method of non Darcy coefficient, the deliverability model suitable for the target block was derived. The model is simple and practical, with clear application conditions. At the same time, it can reduce the time of pressure gauge under construction, reduce the practice risk, and has important guiding significance for the rational development of gas reservoir.