The utility model relates to a front-mounted tail gas post-processing system and a harvester, the front-mounted tail gas post-processing system is used for an engine arranged between a cab and a fruitbox of the harvester, the front-mounted tail gas post-processing system comprises a tail gas post-processing device and a urea pump tank assembly; the tail gas post-processing device is detachably connected to the harvester and located at the front upper end of the engine, the urea pump tank assembly is connected with the tail gas post-processing device, arranged on the left side or the right side of the tail gas post-processing device and communicated with an exhaust port of the engine, and an exhaust tail pipe is arranged on the tail gas post-processing device. By means of the tail gas treatment device, the NOX content, PM and PN indexes in tail gas are well controlled, tail gas emission reaches the higher emission standard, tail gas emission air pollution is reduced, the space betweena harvester cab and a fruit box is well utilized, the arrangement difficulty is lowered, and the influence of vibration of the whole harvester on the post-treatment device is reduced.