Post-treatment two-stage urea injection system

The embodiment of the invention discloses a post-treatment two-stage urea injection system which is used for improving the reaction efficiency of NOx, so that the NOx is discharged outwards under the condition that the NOx is fully reacted, and the pollution to the environment is reduced. According to the post-treatment two-stage urea injection system, an oxidation catalyst is connected with an integrated nitrogen-oxygen particle trap through a first breather pipe; the first breather pipe communicates with a first-stage urea nozzle; a first NOx sensor is installed on the first breather pipe; the integrated nitrogen-oxygen particle trap is connected with a tail gas aftertreatment system through a second breather pipe; the second breather pipe communicates with a second-stage urea nozzle; the second NOx sensor is installed on the second breather pipe; the urea injection control system controls the injection amount of urea in the first-stage urea nozzle according to the NOx concentration in the first breather pi