Raw materials of AdBlue® / DEF  are urea crystal and ultra-pure water. The suitable selective catalytic reduction (SCR) system should be selected in the exhaust treatment. And the system must rely on AdBlue® to deal with NOx in the exhaust gas , use of DEF in engine exhaust gas gasification to produce ammonia, selective catalytic reduction of reductant as diesel motor vehicle exhaust, so that the tail gas of nitrogen oxides into harmless water vapor and nitrogen, reduce emissions. Therefore, AdBlue® / DEF can be said to be a necessary product for heavy truck, bus and other diesel vehicles to meet the fourth even five national emission standard.