Abstract: The capacity of a vertical metal tank is usually measured when the tank is empty. If the tank is filled with liquid, the tank body will expand due to the static pressure of the liquid, which will increase the tank capacity. Generally, the static pressure correction value is 0.016%～0.21% of the total volume, which is introduced in capacity tables. For safety of the tank body, one or more reinforcement rings can be installed on the upper part of the tank. The reinforcement rings could affect the correction of liquid static pressure. This paper analyzes the effect of reinforcement rings theoretically and discusses how to calculate the correction of liquid static pressure.