Abstract: For the common water drainage-gas recovery technology, selection of rational production parameters, at the same time of selecting small tubing size, is very important to prolong the flowing production period of gas well. Therefore, it is necessary to analyze the relationship between production parameters and rational tubing size. This paper analyzes the relationship between production parameters, such as gas production rate and wellhead pressure, and critical tubing size, and presents the curve of relation between production parameters and tubing sizes according to a real gas well. The results achieved can be used to guide field production.