The development of economy in developing countries is expected to contribute mostly to the growth of world energy consumption. Using environment Impact-GDP-Technology (IGT) decoupling model, we carry out a comparative study on the decoupling trends of economic growth and energy consumption for both developed and developing countries in past five decades (1965-2015). The results indicate that the decoupling indices of developed countries are superior to that of developing countries. The specific performances are: (1) The de coupling indices of developed countries are shown to be stable and tend to approximate absolute decoupling; (2) The decoupling indices of developing countries fluctuate in the relative decoupling interval. On this basis, this research employs grey relational analysis (GRA) to explore the reasons resulting in the difference of decoupling indices from the perspective of technical progress, industrial structure and economic growth pattern. The findings show that: in developed countries, technical progress factor exerts greatest influence on decoupling indices, followed by industrial structure and economic growth pattern; in developing countries, industrial structure and economic growth pattern have greater impact on decoupling indices than technical progress. Based on research conclusion, this research offers developing countries relevant policy suggestions for energy saving and emission reduction in the future.