According to the request of emission reduction of industry and total ammonia amount control in 12th five-year plan periods,this paper investigates the comprehensive evaluation methods of emission reduction technologies---a case study of nitrogen fertilizer. Aiming at the problems of domestic environmental technologies evaluation methods are mainly based on experts’qualitative estimate and lack of comprehensive evaluation methods, cost benefit analysis and analytic hierarchy process with grey comprehensive evaluation method were combined,a kind of evaluation method of best available technology for emission reduction of ammonia in nitrogen fertilizer industry was developed．The modeling process of the mathematical model of analytic and grey integrated evaluation method was provided with an application example analyzed．