The present invention relates to phenyl [a]indole[2,3-g]quinolizine compounds represented by formula (I), a preparation method therefor, a pharmaceutical composition, and applications thereof. Specific applications are applications in the preparation of drugs for treating diseases related to a proprotein convertase subtilisin Kexin-9 (PCSK9), comprising the applications in the preparation of drugs for treating hyperlipemia, hypercholesterolemia, hypertriglyceridemia, fatty liver deformation, atherosclerosis, obesity and other metabolic diseases.