The invention relates to a fused cyclic gamma-amino acid derivative, a preparation method of the fused cyclic gamma-amino acid derivative, and an application of the fused cyclic gamma-amino acid derivative to pharmaceuticals, and particularly relates to the fused cyclic gamma-amino acid derivative shown as in the formula (I), or a stereoisomer, a solvate, a metabolite, a prodrug, a pharmaceutically acceptable salt or co-crystal of the fused cyclic gamma-amino acid derivative, a pharmaceutical composition comprising the fused cyclic gamma-amino acid derivative, and the application of the compound or composition to the field of analgesia, wherein the definitions of various substituent groups in the formula (I) and the definitions in the description are the same.