Abstract: Suitable fertilization which can build up favorable plant morphology and increase the quantity of blooming is one of the most important factors on growth of flower. Petunia hybrida Vilm. is one of the most important potted flowers, and a parterre decorative plant in the world. Based on the “3414” fertilizer experiment design, a pot experiment in greenhouse was conducted to study the effects of NPK fertilizers on growth, ornamental quality and optimum fertilizer rates of petunia. Data of plant height, crown diameter, present flowers, number of total flowers and dry weigh were measured. The results show that both the nitrogen fertilization and the phosphorus fertilization play important roles on petunia growth and development, while the potassium fertilization has obvious effects at the flowering stage. Coordinated applications of nitrogen, phosphorous and potassium promote petunia growth significantly, and their effects on the growth of petunia are in order of NPK. Through establishing the fertilizer efficiency model based on number of total flowers, it is showed that the recommended fertilizer amounts of N, P2O5 and K2O for the pot application are 0.61 g/pot, 0.26 g/pot and 0.34 g/pot (each pot filled with 1.5 kg substrate). The suitable ratio of N: P2O5: K2O is 1: 0.43: 0.56.