Provided is a tail gas post-treatment mixing device (3), comprising a shell (31), a mixing tube (32) located inside the shell (31), and a partition plate (33) fixed at the periphery of the mixing tube (32), wherein the partition plate (33) separates the shell (31) into a first space used to be in communication with a first post-treatment carrier assembly and a second space used to be in communication with a second post-treatment carrier assembly; the partition plate (33) comprises a first plate sheet (331) located at one side of the mixing tube (32), a second plate sheet (332) located at the other side of the mixing tube (32), and a third plate sheet (333) connecting the first plate sheet and the second plate sheet, with the third plate sheet being provided with a through hole (334) for the mixing tube (32) to pass through; and the mixing tube (32) comprises a first tube part (321) located in the first space and a second tube part (322) located in the second space, and the first tube part is provided with at least two first openings (3211) respectively located at two sides of the first tube part. The tail gas post-treatment mixing device further comprises a first shielding plate (381) and a second shielding plate (382) respectively shielding the front end of the first opening, so that the vast majority of exhaust flow needs to bypass the first and second shielding plates (381, 382) to enter the first opening (3211).