Abstract: Empirical coefficient is the important parameter of single point method for gas well productivity evaluation, so how to select the empirical coefficient solving method is of great significance to improve the accuracy of single point method.In this paper, Yanchang Gas Field was taken as an example.Its empirical coefficient was selected by means of optimization method (the sum of the variance between the actual absolute open flow (AOF) and the calculated one is minimum), and the relational expression between empirical coefficient and formation capacity was established.It is shown that the empirical coefficient and AOF average error of pressure squared method which are calculated by means of the optimization method are 0.94 and 5.7% and those of pseudo-pressure method are 0.8 and 7.8%.The errors of both methods are lower than that of conventional methods, and the former is much better.And it is also indicated that the empirical coefficients of gas wells in Yanchang Gas Field are all higher than 0.8.The porous flow in the formation is mainly Darcy flow, the pressure drop consumed by high-speed non-Darcy flow is less, and its logging formation capacity (kH) and empirical coefficient satisfy the following conditions, i.e., in the case of kH < 29 D∙m, it is linear relationship between formation capacity and empirical coefficient and empirical coefficient increases with the increase of formation capacity, while in the case ofkH≥29 D∙m, empirical coefficient is 0.94.