The present invention discloses a soft gelatin capsule formulation of a 15-keto-prostaglandin compound, which comprises: a soft gelatin capsule shell comprising gelatin and sugar alcohol as a plasticizer, and a mixture comprising a 15-keto-prostaglandin compound and a pharmaceutically acceptable vehicle which is filled in the shell. By encapsulating the 15-keto-prostaglandin compound in the specified soft gelatin capsule shell, stability of the compound is significantly improved.
