As the first RNA catalyst (ribozyme) discovered in nature twenty years ago, group Ⅰ intron has been extensively studied to understand catalysis, structure and folding of the catalytic RNA, which fundamentally contributes to the current understanding of RNA structure and function. Most of the major topics in group Ⅰ intron study, emphasizing on the tertiary structure and folding issues that has bloomed in the past several years are reviewed.