Control method for UREA injection of SCR system

Component injection control method of the SCR system of the present invention comprises a step for injecting the dosing element in the SCR catalyst module to test the duty value; After the spraying step, the step of detecting the NOx amount and ammonia amount by the NOx sensor provided at the rear end of the SCR catalyst; On the basis of the detected NOx amount and ammonia amount calculating an injection element; And according to the injection quantity correcting element with a duty value of a dosing module, it may include a.