A exhaust after treatment system for engine

The utility model discloses an exhaust after treatment system for engine. Exhaust after treatment system including the premixer pipeline of injecing exhaust flow path, arrange baffle in exhaust flow path and the reductant sprayer that communicates with exhaust flow path fluid. The baffle is arranged in the premixer pipeline, and the premixer pipeline includes premixer entry, transition section section and mixer outlet in advance. The transition section section is arranged at the premixer entry with in advance between the mixer outlet. Premixer entry and engine fluid intercommunication. The reductant sprayer is located the low reaches and mixer outlet's the upper reaches in advance of baffle. The utility model discloses a purpose that disclosed premixer pipe arrangement was realized is the just favorable carminative mobile situation that produces the expectation in exporting the festival section. The mobile situation that produces helps avoiding being moved and the formation of the deposit that the backpressure aroused that changes by non -uniform flow.