Collagen was extracted from different species of grass carp and used to study amino acid compositions and thermal stability. The result of a correlation analysis between the amino acid compositions and denaturation temperatures of various collagens showed that the degree of hydroxylation of proline, the content of alkaline amino acids, polar amino acids with charge, and total polar amino acids were positively correlated with the denaturation temperature for collagen. However, the content of imino acids and nonpolar amino acids showed an inverse correlation with the denaturation temperature (p < 0.01). The mathematical model of correlation between amino acid distribution and denaturation temperature of collagen was established by step-wise regression analysis using SAS software, which accurately forecasts the denaturation temperature of fish collagen. At the same time, the influence of solvent environment, including infiltration degree of water, pH, ionic strength, and ion species, on the thermal stability of fish collagen was investigated. The results showed that the thermal stability of fish collagen underwent a remarkable decrease with increase in the infiltration degree of water and ionic strength as well as a decrease in pH of the solvent.