The research aimed to investigate the effects of nitrogen，phosphorus and potassium combined application on the growth and development of carrot，and provide scientific basis for standardized carrot fertilization.Using “3414” design，field experiments were carried out to determine the botanical characteristics and nutritional quality of carrot ‘Yanhong 2’.According to different fertilization levels，the fertilizer requirements of carrot nitrogen (N)，phosphorus(P)and potassium(K)were analyzed，and the optimal application amount of N，P and K for carrot was evaluated by membership function.The results showed that the appropriate fertilizer application rate could promote the botanical characters of carrot such as root length，root weight and root roughness，the photosynthetic characters of SPAD，net photosynthetic rate and the quality characters of total phenol，total flavonoid and vitamin A.The effect of N，P and K on carrot yield was N>P>K.Under N1P2K1 treatment，the highest SPAD value was chlorophyll content，the highest net photosynthetic rate was CO₂ 19.2 μmol/(m2·s)at N3 level，the highest water content，total phenol content and vitamin A content were reached at N2P2K2 level，and the highest soluble sugar content was 38.15 mg/g at N1P1K2 level.The highest values of soluble protein content and total flavone content were 7.64 and 304.16 mg/g，respectively，at N2P1K2 level.The botanical characters，photosynthetic characters and quality characters were analyzed and evaluated by correlation analysis and membership function method.The characteristics of plant height，root weight，total phenol，total flavone and vitamin A，which had great influence on carrot quality，were considered comprehensively，which showed that yield and quality occupied an important position in production practice.The comprehensive properties of N2P2K2 were evaluated by membership function，and the ratio of N2P2K2 was N∶P2O5∶K2O= 60∶82∶75.