The embodiment of the invention discloses a tail gas treatment system and a control method. When an engine is just started, the temperature of a first catalyst can be rapidly increased to the workingtemperature through heat generated by fuel combustion, then a first exhaust circuit is opened, and a nitrogen oxide adsorber and the first catalyst are used for reducing emission of NOx in tail gas; and when the temperature of a second catalyst reaches a high temperature, a second exhaust circuit is opened, and emission of NOx in engine tail gas is reduced through the nitrogen oxide adsorber and the second catalyst, heat losses caused when tail gas flows through the first catalyst can be reduced, due to the fact that the second catalyst is far away from the engine, the engine back pressure islowered, and fuel of the engine is fully burned.