This experiment was conducted to study the effects of dietary protein to lipid ratio on whole-body protein content, muscle amino acid composition, whole-body lipid content and muscle fatty acid composition of blunt snout bream (Megalobrama amblycephala) in different growth stages. Six experimental diets were formulated with different protein to lipid ratios, which were 2.63 (P26.93/L10.24; P was the percentage content of dietary protein, and L was the percentage content of dietary lipid), 3.20 (P28.50/L8.91), 4.07 (P30.09/L7.39), 5.33 (P31.63/L5.93), 7.25 (P33.78/L4.66) and 10.64(P35.63/L3.35), respectively. Blunt snout bream in 3 growth stages with the initial average weight of (10.37±0.69) g/fish (juvenile fingerlings), (35.07±0.45) g/fish (medium fingerlings) and (101.65±1.82) g/fish (premature fish) were launched in circular aquarium system (juvenile fingerlings) and conducted in pond cages (medium fingerlings and premature fish) for 64, 85 and 56 days, respectively. Six groups were divided into each growth stage with 4 replicates, and each replicate had 20 fish. The results showed as follows: with the dietary protein to lipid ratio increasing, the special growth ratio, protein deposition rate and feed conversion rate of blunt snout bream in 3 growth stages all showed a trend of firstly rise and then decline, and the extreme values were all found in 5.33 group. Whole-body protein content and muscle amino acid composition of blunt snout bream were mainly influenced by the growth stage. The smaller fish had the lower whole-body protein content, while the amino acid content of muscle was higher. When dietary protein to lipid ratios were 4.07 to 5.33, the blunt snout bream gained the higher protein and amino acid deposition. There was a positive correlation between whole-body protein content and dietary protein to lipid ratio for the same stage. Dietary lipid content and fatty acid composition had a great impact on the whole-body lipid content of blunt snout bream. Changes in water temperature also had some influences on the whole-body lipid content of blunt snout bream, and the lower temperature was good for the body lipid deposition. There was a power function relationship between whole-body lipid content and dietary protein to lipid ratio for the same stage. Compared with dietary fatty acid composition, the muscle fatty acid composition of blunt snout bream had a certain degree of change, which illustrated that blunt snout bream had some ability to transform the dietary fatty acids, and this ability strengthened with the growth of blunt snout bream.