In order to analyze the effect of different amino acid residues on the thermal stability of natural collagen. The heterotrimer abc,which better mimics the low-imino content of natural collagen,was used as the research host. Different mutant collagen sequences were designed,propensities of different amino acids were considered as their thermal stability measured with circular dichroism. At the same time,the frequency of amino acids in natural collagen sequence was calculated. Based on the propensities,local stability of type Ⅰ collagen was predicted computationally. The results show that Ala,Leu and Glu at X-position and Gln,Thr,Ala and Arg at Y-position have both high propensities and high frequently occurring frequencies. The predicted local stability suggested that type Ⅰ collagen may be divided into two types of regions. One type is high-stability regions for folding of the secondary structure and the other type is low-stability ones,which may play an important role in dynamics of biological processes. The study shows that amino acids with high thermal stability and high frequency play a key role in the stability of natural collagen.