This study analyzed that technological competition, variety and simility of Green IT fields using patents data. To achieve this, we limited range of Green IT that reduction of energy, eco-friendly technology. Therefore we conducted analysis of patents that power saving systems, light control system, smart system, cloud computing and green house/eco systems. As the result of that, power saving field was the most developed. The simililarty of power saving and cloud computing systems are very high and similiarities of light control system, green house/eco systems and smart system were very high.