Tail gas treatment device with flow regulating device and system

The utility model discloses a tail gas treatment device with a flow regulating device and a system. An exemplary tail gas treatment device comprises a housing, a first post-treatment part located in the housing and the flow regulating device located in the housing and at the upstream of the first post-treatment part, wherein the flow regulating device is configured to uniformly distribute tail gas to a first inlet surface of the first post-treatment part; the flow regulating device comprises a flange and the flange defines a first chamber and a second chamber in the housing; the flow regulating device further comprises a pipe fitting and the pipe fitting extends through an inlet end cover and the flange; the pipe fitting comprises a plurality of first through holes in the first chamber and a plurality of second through holes in the second chamber; the pipe fitting further comprises a pipe fitting end cover with a plurality of third through holes; a downstream end of the pipe fitting defines first length of a second pipe fitting part, and the first length is smaller than second length in the second chamber.