Ribozyme is a kind of RNA with self-catalytic activity which was found in 1980s. To block the expression of harmful genes, including self-mutation and heterogenous pathogens, in the human cell at level of nucleic acids, this is a very specific therapy with the least harm to human body. The natural ribozyme has the cis activity, but it can be engineered with trans activity. This is the base to design ribozyme with therapautic activity. In this paper, the authors mainly discussed the hammerhead and hairpin ribozymes, and the principles involved in application of ribozyme as therapautic agents were also given.