Abstract: Analysis of the secondary structures of mRNAs which encode mature peptides shows that the location of each codon in mRNA secondary structure has a trend,which appears to be in agreement with the conformational property of the corresponding amino acid to some extent.Most of the codons that encode hydrophobic amino acids are located in stable stem regions of mRNA secondary structures,and vice versa,most of the codons that encode hydrophilic amino acids are located in flexible loop regions.This result supports the recent conclusion that there may be the information transfer between the three-dimensional structures of mRNA and the encoded protein.