Abstract: In the case of natural fouling of insulators, the salt ash, the particle size, the surface elemental composition, and the particle morphology of the upper and lower surfaces would change during the process of surface contamination. In this paper, the insulator string of overhead transmission lines in Xuzhou, Jiangsu Province is taken as an object to test and analyze the physical and chemical characteristics of the surface contamination of suspension insulator insulators. Meanwhile, the surface contamination characteristics of insulator in Xuzhou area are discussed. The key findings are as follows: the insulator equivalent salt deposit density and non-soluble deposit density are related to weather, and the dirt accumulation achieves maximum value in February, which has a great relationship with the main surrounding pollution sources. In the cement polluted area, Xuzhou, the filthy degree on the upper-surface is larger, the filthy degree on under-surface is relatively smaller; The particle size, composition and content of the fouling on the surface of insulator differ greatly under different environments.. Conclusion can be used as reference basis of insulators' operation and maintenance in cement polluted area.