Based on the brief description of the basic connotation of subheading and coordinate indexing of subjects/subheading (subheading attachment indexing for short), the paper concretely analyzed the realization methods of automatic subheading attachments for Medical Text Indexer（MTI）, which is the medical text indexing tool developed by United States National Library, including "Jigsaw puzzle" methods, rule-based methods, and statistical method, then it tries to put forward research directions of Chinese biomedical literature automatic indexing of subheading attachment.