Abstract: The paper established the material balance and energy balance dynamic models of underground gas storage filling system and selected the downhole as nodes to divide the filling system into two parts-inlet flow and outlet flow. With the established node model of vertical conduit flow inlet flow and outlet flow of stratal filtrate, a calculation provided the dynamic characteristic parameters of inflow and outflow, which can be used to analyze the gas filling status. Regarding the vertical gas flow from ground to the downhole as a semi-steady state flow, the downhole pressure is calculated by "mean temperature & mean deviation coefficient" and "Cullender & Smith" methods. Adopting the surface index and flow-related surface index into the radial flow from the downhole to the stratas, the gas filling volume can be calculated. Taking the Directional 4-2 and Directional 3-6 in some 36 Wellfield as an example, group calculation of the inflow and out flow was made, and the result basically agreed with the practical conditions.