The invention discloses a triazole derivative having an HSP90 (Heat Shock Protein) inhibiting activity, as well as a preparation method and an application of the triazole derivative. Specifically, the invention relates to the triazole derivative having a structure as shown in a formula (I), a stereisomer of the triazole derivative and a pharmaceutically acceptable salt, wherein the definition of each substituent group in the formula (I) and the definition in a description are the same. The compound with a novel structure has the HSP90 inhibiting activity, can be used to cure cancers, neurodegenerative disorders, inflammation diseases, autoimmune diseases, ischemic brain injuries and the like, and has a broad application prospect.