Urea spray selective catalytic reduction control system

A urea spray selective catalytic reduction ("SCR") control system includes an SCR catalyst provided in a discharge pipe of an engine, a dosing valve for injecting urea water at an upstream side of the SCR catalyst, and NOx sensors, wherein the system controls injection of the urea water from the dosing valve. The system includes a plurality of NOx model maps corresponding to an atmospheric pressure condition, an outdoor air temperature, and an engine water temperature, and determines an amount of NOx from each NOx model map on a basis of detection values of an atmospheric pressure detector, an outdoor air temperature detector, and an engine water temperature detector, and controls an amount of injection of the urea water from the dosing valve on a basis of the amount of NOx thus determined.