It is important to clarify the influence of various types of dust on the insulation performance of epoxy resin. In this paper

three kinds of material powders are used to simulate the dust types that may exist in gas-enclosed insulation equipment. Surface charge characteristics of each group of dust-attached samples are measured

and AC flashover test is carried out in a mixed C

4

F

7

N-CO

2

gas environment. The results show that the charge accumulation of metal dust-attached samples is the largest

and that of insulating and semiconductor dust-attached samples is similar; the charge dissipation rate of metal dust-attached samples is the fastest

and that of semiconductor dust-attached samples is the second

while that of insulating dust-attached samples is

the slowest. The flashover voltage along the surface of metal dust-attached samples increases with the decrease of diameter of particle grain（d）

while that along the surface of semi-conductor and insulator ash-attached specimens decreases. Compared with the samples after surface charging operation

the flashover voltage of non-charged samples（original samples） is lower. The effects of different materials and d values of dust attached to the surface of epoxy resin insulation on its surface charge characteristics and flashover characteristics along the surface and the relationship between them are described.