Basin-type insulator is the most vulnerable component of gas insulated switchgear（GIS）. In this work

thedefect types of GIS are firstly analyzed

and the failure rate is calculated. Then

the factors influencing the surface flash-over of basin-type insulator

including the metallic particle contamination

the spacer surface defect as well as the sur-face charge

are systematically elucidated. The charging process and forces applied on the metallic particle is present-ed;the motion characteristics and suppressing techniques for metallic particle are discussed in detail. Regarding thesurface defect of basin-type insulator

the defect types

the evolution of deterioration and detecting methods are over-viewed. In the case of DC voltage

charges are often accumulated around spacer surface

leading to the surface flash-over. The mechanism

the measurement methods as well as the dynamics of space charge are also summarized in thiswork. Furthermore

to address the surface flashover issue

the suppressing techniques

including the profile optimi-zation

the use of dielectric coating and the functionally graded material

are comparatively analyzed. Their character-istics and applications are discussed. Both the advantages and drawbacks of them are summarized. Finally

severalsuggestions on spacer design have been proposed for with respect to the ongoing UHV transmission project in China.