Abstract: The paper using linear theory, analyses whether tank roof has any impact on shell stress. The shell stress for each layer can be derived from the undetermined coefficient in its flexibility equation obtainable by analysing and calculating the shell boundary conditions and roof boundary conditions for arc/floafing roof tanks? It can be seen from the linear equation that the main factor impacting shell stress is the undetermined coefficient in the flexiblity equation, and that this coefficient is dependent on the weight, shear force and bending moment of the tank roof, as well as on the tank size and liquid level. With 100, 000 m³floating roof and arc roof tanks as examples, the autor proves that liquid level places a dominant role on the impact on shell stress, while the impacts of roof weight, shear force and bending moment on shell stress are ignorable.