Technology trends of coal gasification were studied through patent analysis. The patents published or registered in Korea, U. S. A., Japan and Europe, and administered by the World Intellectual Property Organization from mid 1970s to 2010 were analyzed based on the application tendency, patent share, major applicants and their activity indices, and market power, etc. Japan and U. S. A. led the patent activities in the early phase of technology development, but major applicants had been diversified globally since 2000. Portfolio analysis revealed that the technology was under developing period. The analysis showed that the most active R&D had been focused on gasifier development. Technology competitiveness was analyzed via indices such as cites per patent, patent impact index, technology strength and patent family size, etc. Key patents were extracted through quantification based on patent family size and cites per patent. The technology flow was figured out to reveal the technology trends.