It is required to analyze the contamination deposited characteristics for the external insulation configuration in ±800 kV ultra-high voltage direct current transmission lines. The contaminant samples were obtained from ±800 k V Chu-Sui UHVDC transmission lines in 2013 and 2014. The distribution of contaminant equivalent salt deposit density（ESDD） level was analyzed to investigate the pollution degree

the influence of DC pole

and part of insulator. Measurement results of contaminant samples show that the maximum value of ESDD is 0.192 9 mg/cm

2

and the minimum value of ESDD is 0.000 7 mg/cm

2

. the ESDD value of 76% samples is less than 0.025 mg/cm

2

. The contamination deposited level of insulator string is not affected by the DC pole. ESDD

values of both ends in the insulator string are much higher than those of middle part. ESDD values of small umbrella are higher than those of big umbrella. Upper surface ESDD values of 54.8% umbrella samples are not less than those of lower surface

which is different from the ceramic and glass insulator. The pollution degree of ±800 k V Chu-Sui UHVDC transmission lines is light overall

and the external insulation configuration is reasonable.