Method of the assessment on the rationality of nitrogen(N)and phosphorus(P)fertilization were set up based on the concepts of environmental safety threshold and index of fertilization in order to analyze the rationality of N and P fertilization in Anhui province.The results showed that there were three periods for use of N and P fertilizers with trends of fast,updown and smooth increasing from 1987 to 2015; at the end of 1980’s the N fertilization was reasonable and P fertilization was short; after 1990 N was overused and P input changed from rationality to overuse.In 2015,half of the 16 prefecturelevel cities in Anhui province belonged to N fertilization rationality areas,the other half belonged to N shortage or overused areas; a lot of cities overused P except 5 cities belonging to P shortage or reasonable.So it is a first task for most of cities in Anhui to reduce the use of phosphorus to a reasonable level.