The invention discloses a liquid ring roots vacuum unit, which is characterized by comprising a roots pump and a liquid ring pump, wherein the bottom end of the roots pump is provided with an air inlet, a filtering device is arranged in the air inlet, a rotor and a shaft I are arranged in the pump cavity of the roots pump, the middle part of the rotor is provided with the shaft I, the bottom of the roots pump is provided with a vent port I, the roots pump is connected with the liquid ring pump, a control device is arranged between the roots pump and the liquid ring pump, a liquid ring, a shaft II and an impeller are arranged inside the liquid ring pump, the shaft II drives the impeller and the liquid ring to rotate, and the top end of the liquid ring pump is provided with a vent port II. The liquid ring roots vacuum unit has the advantages that the roots pump is combined with the liquid ring pump, so that high efficiency and energy conservation can be realized, the structure is compact, the vacuum degree is high, and the discharge capacity is large; and by setting a charcoal filter layer, the absorbed air is more clean, the liquid ring roots vacuum unit is applicable to the vacuum drying, petroleum chemical industry, metallurgy and chemical fiber industry, and the application range is wide.