The invention relates to an intelligent dynamic sealing liquid storage tank with a flexible capsule and a using method of the intelligent dynamic sealing liquid storage tank with the flexible capsule. A liquid inlet and a venting port are formed in the upper portion of the liquid storage tank, a liquid inlet solenoid valve is arranged on the liquid inlet, a vent valve is arranged on the venting port, and a liquid outlet is formed in the lower portion of the liquid storage tank. A liquid outlet solenoid valve and on-line moisture detectors are sequentially arranged on the liquid outlet in the liquid outlet direction. An air tube and an electric contact liquid level meter are further arranged on the liquid storage tank, the flexible capsule is arranged in the liquid storage tank, and the surface of the capsule is surrounded by liquid. An inner cavity of the flexible capsule is communicated with outside atmosphere through the air tube, and the liquid inlet solenoid valve, the liquid outlet solenoid valve, the on-line moisture detectors and the electric contain liquid level meter are electrically connected to a control module. Due to the fact that the inner cavity of the flexible capsule is communicated with the outside atmosphere through the air tube, the breathing effect of the flexible capsule plays a role in compensating and balancing volume changes caused by changes of the liquid level in the liquid storage tank, and dynamic sealing is achieved.