Abstract:This paper introduced a current situation of China’s coal fired power plant using SCR denitrification facility and the policies and requirement according to the regulations of the state for ultra low emission of coal fired unit.In order to make sure that SCR denitrification facility meet the discharge standard,this paper analyzed several common problems that might happen such as catalyst plugging and wearing,air pre heater blocking,ammonia in short supply and low efficiency of denitration,and explained causes that might contribute to above problems such as unreasonable flow field,low load running boiler in a long term,low temperature flue gas,low temperature at the cold end of air pre heater,poor performance of catalyst,insufficient output of evaporator and changing coal quality,etc.