Choroidal thickening spectrum diseases include pachychoroid pigment epitheliopathy(PPE)central serous chorioretinopathy(CSC), pachychoroid neovascularization(PNV)and polypoidal choroidal-vasculopathy(PCV). PPE refers to permanent abnormal increase in choroidal thickness. It is manifested as dilatation of large choroidal vessels(Haller layer)oppressing the surrounding middle vascular layer(Sattler layer)and capillary layer(Choriocapillaris layer), resulting in insufficient blood supply to the retinal pigment epithelium and causing a series of retinitis pigmentosa. The other three diseases can progress from the pachychoroid pigment epitheliopathy. The study of the pathogenic characteristics and imaging changes of choroidal thickening spectrum diseases will help to explore the diseases' pathogenesis, providing reference for early clinical diagnosis, prevention and treatment.