The invention discloses a simple waste gas filtering device which comprises a cylinder, wherein two partitioning plates are fixed in the middle of the cylinder; a through groove is formed in a side wall of the top of the cylinder between the two partitioning plates; a driving motor is arranged between the two partitioning plates; the driving motor is fixed on a partitioning plate on the left side; the output shaft of the driving motor penetrates through the partitioning plate on the left side; a rotating impeller is fixed on the driving motor; an annular groove is formed in the left end of the cylinder; a left connector is sleeved by the annular groove in an insertion manner; the left connector is fixedly connected with the right end surface of the annular groove of the cylinder through a bolt; the cylinder between the left connector and the partitioning plate on the left is a left cavity; inner threads are formed in the inner side wall of the right end of the cylinder; a right connector is screwed with the inner threads; an extended side which extends outwards in the radial direction is arranged on the outer side wall of the middle part of the right connector; the extended side leans against the right end surface of the cylinder; an exhaust port which extends rightwards is formed in the right end of the right connector. The simple waste gas filtering device is small in size, small in occupation space, good in filtering effect and applicable to small-size production environment.