Water ring vacuum pump unit

The invention relates to a water ring vacuum pump unit. The water ring vacuum pump unit comprises a first roots vacuum pump, wherein an air inlet pipeline is connected onto the first roots vacuum pump; one end of the air inlet pipeline is an air inlet; a first ball valve is arranged on the air inlet pipeline; a butterfly valve is arranged at the part, positioned between the first ball valve and the first roots vacuum pump, of the air inlet pipeline; the part, positioned between the butterfly valve and the first roots vacuum pump, of the air inlet pipeline is connected with a water ring vacuum pump through a first connecting pipe; the water ring vacuum pump is connected with a second roots vacuum pump through a second connecting pipe; the first connecting pipe is communicated with the second connecting pipe; the second roots vacuum pump is connected with a third roots vacuum pump through a third connecting pipe; the third roots vacuum pump is connected with the first roots vacuum pump through a fourth connecting pipe. The water ring vacuum pump unit has the advantages that the air inflow is small, dust in a drum is not easy to suck, the blockage of the vacuum pumps is not caused and the failure rate of equipment is reduced.