The large-scale application of silicon rubber (SR) line insulators in China has improved the outdoor insulation level in power systems significantly. China has become the first country in which the organic outdoor insulation dominates UHV AC and DC transmission systems. The organic outdoor insulation is the hot spot in the field of research and application of outdoor insulation in power systems, and SR composite insulator is the representative. In this paper, the operational problems of composite line insulators are classified and analyzed. And the market share and competitiveness of composite insulators are compared with those of porcelain and glass insulators. The obvious advantages, prospect of development and existing problems of the application of composite insulators in substations and converter stations are discussed. Some other problems and opportunities in the development of organic outdoor insulation are analyzed.