Abstract: Extension of agricultural science and technology is an important way to translate scientific and technological achievements into practical productive forces. It makes a link and a approach to promote the development of agricultural science and technology. However, the lower conversion rate of agricultural science and technology achievements has become the bottleneck restricting the development of modern agriculture in China. This paper is mainly to compare the extension service system of domestic and overseas agricultural science and technology, and points out their advantages and disadvantages. Base on the existing problems on extension service system of agricultural science and technology in China, this paper put forward the illumination from the advanced mode in foreign.