Disclosed are a pharmaceutical composition of a fused tricyclic γ-amino acid derivative and the use thereof. The pharmaceutical composition comprises : (i) the structure as shown in formula (I) or a pharmaceutically acceptable salt thereof, as an active substance, wherein the weight percentage is 1%-45%; (ii) optionally one or more fillers, wherein the weight percentage is 50%-95%; and (iii) optionally one or more lubricants, wherein the weight percentage is 0.1%-5.5%. The sum of the weight percentages of all components is 100%. The structure of the pharmaceutically acceptable salt of the structure as shown in formula (I) is as shown in formula (I-A).