Abstract: In the 1970s, China's energy supply was mainly coal and oil. Natural gas, an important source of energy, was still ignored by most people at that time. The prevailing "monism" theory of oil-derived gas then held that coal-producing areas wouldn't produce natural gas. However, Chinese scholars first put forward the concept of coal-derived gas in 1978. In the next 40 years, the coal-derived gas geological theory in China has gone through the whole process of introducing, absorbing, innovating, developing, forming system and guiding the rapid development of natural gas industry. Its contents include the index system of gas source identification, the accumulation mechanism and distribution law, and the evaluation and prediction technique of coal-derived gas, etc. The application of the theory has accurately predicted more than five large gas fields of over 100 million m³ magnitude, making the proportion of coal-derived gas in natural gas of China soar from 10% to 67%, and propelling the rapid growth of natural gas reserves and production in China. Apparently, the theory has important strategic significance to Chinese natural gas industry and has made fundamental contribution to the fast development of gas industry in China.

Key words: natural gas, coal-derived gas, coal-derived gas geolgical theory, monism, dualism, strategic