Abstract:LEAFY is an important regulator of floral meristems genes in higher plants. To investigate its origin and evolution, a LEAFY homologs with length of 2 866 bp was cloned from Capsella bursa-pastoris genome using the conserved primers from Arabidopsis thaliana LEAFY gene. Sequence analysis indicated three exons with the length of 457 bp, 407 bp and 411 bp. These exons encoded a protein of 424 amino acids. The single exon was more than 90% homologous to A. thaliana LEAFY gene, and the amino acid homology was 86%. When compared to Arabidopsis lyrata LEAFY gene, there was 93 nucleotide substitution in the exons of C. bursa-pastoris, and 74.7% of these mutations located at the third position ofcodon, the amino acid homology reached 90%. Among the three exons, Ds/Dn ratio was 1.9, 2.3 and 6.0. Homologous comparison indicated that the C-terminal amino acids were highly conserved among different plant species while the great variation existed in N-terminal. In addition, the Arg mutation located at 346 in CapLFY gene was speculated to be one of main reasons that caused the ecotypes with different flowering time in C. bursa-pastoris.