The invention discloses a storage tank capable of increasing suction pressure. The storage tank comprises a bracket, a tank body and a tank cover, the bracket is supported on the horizontal ground, and the tank body and the tank cover are connected in a matched mode and arranged over the bracket; and the storage tank is characterized in that an air injection device is arranged on the upward face of the tank cover in the using state, a containing cavity is formed in the tank body, a control valve is installed on the outer-side tank wall of the tank body, the control valve communicates with thebottom of the containing cavity through a bent pipe, and the air injection device and the bent pipe cooperate with each other to enable residual liquid at the bottom of the containing cavity to be drained out through the control valve. The speed that the liquid flows out of the control valve is increased, and the operation difficulty of a user is reduced; and in addition, the appearance is delicate and suitable for appreciation, the whole structure is simple, and the production cost is reduced.