Abstract: The coordinated development of energy consumption, economic growth and environment is an important aspect of sustainable development. How to achieve sustainable economic growth under the double constraints of energy and environment has always been a hot spot in energy economics research. Since the consumption of fossil energy will bring serious environmental externalities and intergenerational externalities, new energy sources have developed rapidly in recent years, and the role of promoting economic growth has become more and more obvious. China's energy transformation has begun, the share of new energy consumption in the energy consumption structure has increased rapidly, and the energy substitution effect is remarkable. To better understand the impact of the energy transition on economic growth,a two-phase economic growth model including the adoption of a backstop substitute and pollution control was studied. Then the optimal proportion of pollution investment accounted for GDP and the equation which optimal switching time satisfies was determined by social welfare maximization. At last the numerical simulation analysis was done to show the effect of some parameters on the optimal switching time and the optimal path of economic growth and the pollution were also given.The results show that at the optimal switching time of the two stage of economic growth patht, the total amount of new energy support will decrease temporarily, but the economic growth rate of new energy supported is higher than that of traditional energy support.If the output elasticity of pollution in the traditional energy supported economy was larger, after the energy substitution occurs，longer time will be needed to control the pollution that has been produced.